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Bring up the subject of cooking eggplant and inevitably the conversation finds its way to salting. Some camps say no, and some camps say yes. On our Kitchn team, Sheela and I represented those two opposing ideas, with Kelli swooping in with a whole new idea all together.

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Eggplant parm, for various reasons, has earned its status as one the most beloved Italian-American dishes. However, if this your only experience with eggplant, let us introduce you to a whole new world. From a smoky roasted eggplant dip to a vegan stir-fry filled with chunks of glazed eggplant, these recipes take a different look at the eggplant and never leave flavor behind.

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Globo Gym employs a highly-trained, quasi-cultural staff of personal alteration specialists. And with our competitively-priced on-site cosmetic surgery, we can turn that Frankenstein you see in the mirror every morning into a Franken-fine!

Of course you’ll still be you in a legal sense, but think of it as a thinner, more attractive, better you than you could ever become without us.

-White Goodman, Dodgeball: The Movie

There are some REALLY bad personal trainers out there. Conversely, there are some AMAZING trainers out there, and they can be the missing link between you and sustainable, consistent progress (or even an elite level of athletic performance).

Back in 2002, I thought I knew everything there was to know about working out (I had been training in a gym for 6 years by then).

Back in 2002, I was also an idiot.

But when I joined a gym that gave me some free personal trainer sessions, my world suddenly got a lot larger. After talking to the trainer and being handed a complete workout and nutrition strategy that was drastically different from what I had been doing for the 6 years prior – and having more success in a month than I had ever had before – I had an epiphany: “I am an ignoramus and a doofus, and I have a lot to learn.”

As I transformed personally and started formulating the ideas that became Nerd Fitness years later, I took a weekend-long personal trainer certification class as required by my local gym, and saw first hand all these soon to be “trainers” that were about to get certified. The range of experience, education, enthusiasm, and professionalism varied DRASTICALLY from person to person.

I came to realize that this particular certification (as with many others) was more of a “start your fitness professional journey” rather than a test of actually qualifying whether you knew your stuff. In short, many certifications are just the tip of the iceberg when determining if your trainer is worth a damn.

A good trainer is worth every penny they charge. (I know my current virtual coach is the best money I spend each month!)

A bad trainer is not only a waste of your time and money, but can set you back months or even years in your training. You’ll get no results, and waste valuable time/money in the process.

Unfortunately, many trainers just don’t give a damn; they’re going through the motions, not providing a program that provides lasting results.

Today, I want to talk about how you can avoid the bad trainers and find the good ones. They’re not cheap, but the amount of money you spend doesn’t always determine their quality.

If you’re going to hire a trainer, here’s how to find a good one.

Make sure you know what you want first

Hire Personal Trainer

First and foremost, understand that your diet is 80-90% of the battle. Even if you worked with a trainer for 60-90 minutes every day, that still leaves you with 22-23 hours per day to screw things up if you don’t eat properly! Hopefully your trainer will also help you craft a nutritional strategy in addition to helping you build a workout strategy that aligns with your goals.

Start by picking your goals first and determine if a trainer you’re paired up with is the right fit for you. Like dating, you can meet somebody who’s amazing but not right for you. If somebody is a competitive marathon runner, they might not be a great powerlifting coach, and vice versa.

So, start with your goals:

  • Are you trying to lose 300 pounds? 30 pounds? Get to 10% body fat?
  • Are you trying to get stronger or hold your first handstand?
  • Do you want to become a competitive powerlifter?
  • Are you looking to run your first marathon?
  • Do you just want to feel better about yourself and enjoy exercise?

These goals will largely determine the type of trainer you’re looking for.

Make sure your trainer has expertise in the area you want to train in. Expertise in one area does not necessarily make them a good fit in another!

After that, you’ll want to think about what you NEED:

  • Are you just looking for a powerlifting coach to show you the basics (squat, deadlift, etc.) so your form is right? Just a few sessions up front and a few later down the line to confirm you’re on the right path might suffice.
  • Are you new to working out or looking to kickstart your first 2 months of training with 2 sessions per week to keep you disciplined?
  • What type of person are you? Do you need more hand holding to do the workout, or more space to take ownership and thrive on your own? Do you need somebody who will cheer you on or do you need tough love from somebody to call you on your bullshit?

Once you set proper expectations with what you want and how long you need a trainer for, then you can pick out one that hopefully will work for you.

How to spot a good trainer

personal trainer stretch

Once you find a trainer you are considering working with, the next steps should always be an in-depth conversation.

Before they do anything else…

They SHOULD be listening to you completely and hearing your story.

They SHOULD ask about any past issues with injuries or experience with exercise. If you’re injured or have any deficiencies, they should know this so they can create a great program for you.

They SHOULD ask you about your nutrition. If they don’t ask about your nutrition, you’re going to be wasting your time.

They SHOULD practice what they preach. They don’t have to be an Olympian, but should have a healthy lifestyle.

They SHOULD tell you about their expertise and how they can help you. They should be able to share past successes of clients with you or point to their credentials and history of success.

They SHOULD set proper expectations. You won’t get ripped in a month, but they can let you know it could take many months to get in shape or build the right kind of habits.

That’s what to look for. Here’s what to watch out for!

Red flags to watch out for

Ahhhhhhh

Beware the “entertainment exercise” trainers with a routine that isn’t catered to your goals. These are the trainers that just try to confuse you with needlessly complex movements and put all their clients through roughly the same cookie-cutter plan because they know it makes them look knowledgeable without actually knowing anything.

“Now balance on this bosu ball while doing these dumbbell squat lunge curls and standing on one foot with your tongue out! Muscle confusion!”

Tough workouts are great, but remember that while it’s easy to get someone tired, it’s hard to help someone improve. Sure, it might elevate your heart rate and tire you out, but if it’s not building towards your goals in a way that you couldn’t do at home, what are you paying for?

They might also have just obtained a basic certification and stopped their education there, relying on ‘conventional wisdom’ rather than doing the research and building the experience. If they say any of the following phrases, run for the high hills:

“Yeah you don’t want to squat too low, it’s bad for your knees.”

“Use this machine, it’s safer for you than the free weights.” (unless it’s due to a pre-existing injury you might have)

“Yes, you should be using mostly your back. That’s why it’s called the back squat”

“Now, you’re going to want to cut the fat out of your diet…”

“These (ab) exercise will burn fat from your stomach in no time” (P.S. You can’t spot reduce fat.)

I have overheard these sound bites from real trainers in real gyms, and it made me weep like the Native American in the 1970s pollution ad.

Your trainer should be results-focused – not focused on scheduling you a new session and keeping you around. I often see clients working with trainers for months and months and that client never looks any different; the trainer is just interested in cashing another check.

Remember, they work for YOU: Don’t let them build a program that doesn’t actually fit your needs. Do you have injuries they’re working around? Do they pick a plan out of a hat and put you through it without focusing on your goals?

Are they actually following along with you? Are they checking your form on movements? Are they encouraging or helping you succeed in the way you want to be encouraged? Or are they scrolling through Instagram models on their phones while you’re doing your sets?

Are they putting in time so they can see you get results? Or are they putting in time so they can check the box and collect your money?

You’re paying money for this person’s expertise and attention – it’s not too much to ask to find somebody who takes those things seriously.

What are good certifications to look for? How much should a trainer cost?

personal trainer night

There are a wide variety of personal trainer certifications and other “credibility indicators.”

The more traditional path – a degree in exercise science or kinesiology may mean the trainer in question is knowledgeable about the human body, but doesn’t speak to any experience they may or may not have coaching in real world circumstances.

Five of the most popular certifications are NSCA, ACSM, NASM, ACE, and Crossfit. T-Nation provides a rundown of the pros and cons from a trainer perspective that we feel is useful insight from a client’s perspective. Be sure to check them out if you want to learn more about what’s behind your trainer’s certification.

CrossFit certifications are completed in a single weekend. While a CrossFit certification does not make a trainer bad (there are plenty of excellent CrossFit coaches out there), it does not guarantee excellence. Here are our thoughts on CrossFit, by the way.

A certification from NPTI – the National Personal Training Institute – is a credential gained from going to a full school on personal training (rather than attending a class or taking a test). While no certification can fully promise excellence, in our experience trainers with NPTI certifications are worth your consideration.

After all that, I’d be remiss if I didn’t mention that I know plenty of trainers who have NO certification that are incredible, and I know other trainers who have the most elite certifications who aren’t that good. A certification can be a starting point, but don’t let it be the determining factor.

In fact, one of the most important things to look for in your trainer isn’t a credential or certification at all, but real experience and an enthusiasm for helping you reach your goals.

Are you looking to powerlift or get into Olympic lifting? Look for someone who has successfully competed in their fields, or someone who actually coaches athletes who do compete! In our view, finding a trainer with proven experience and a track record of performing or coaching (or both) in the area of your goals is the most valuable step you can take to ensure quality. The credential is only a starting point.

Trainers aren’t cheap, but they can be worth every penny. Remember, you aren’t paying simply for their time with you, but for the years and years they’ve spent learning, training, and coaching. It’s the years behind the certification that makes their time so valuable, so expect the cost of a trainer to be significantly more than the cost of a basic membership at your gym.

Find the right coach, and it’s worth every. freaking. penny.

Next steps

Dave During Workout

Here’s my advice: give a trainer 5-10 sessions before making a decision that things aren’t working out (sessions are often sold at a discount in a package). The first session is often exploratory, explanatory, and introductory, and the trainer needs to test your limits and movements to build upon that. This isn’t a “get fit quick” strategy, but rather one that could take months and months for you to find the right person to aid you on your journey. Don’t expect miracles in a day!

A few words of warning:

DO NOT USE YOUR TRAINER AS AN EXCUSE: Too many people will hire up a trainer and give no effort in the gym or the kitchen. Then, when they fail to see results they can turn to their friends and say “man, my trainer is terrible, THAT’S why I’m not losing weight/getting stronger/etc.” This happens so much more often than you’d think. A trainer is a guide, like Morpheus. You have to take the pill and walk through the door yourself.

MAKE CRITICISM CONSTRUCTIVE CRITICISM! Often when the trainer asks them to do something (walk every day, throw away junk food, eat a vegetable), the client/trainee comes back with 1,001 reasons they can’t do that. No compromise, no discussion of possible solutions. Instead of saying “no,” offer an alternative solution and negotiate a plan: “I don’t really like broccoli, do you have a good recipe?”

IF YOU ENJOY WORKING WITH YOUR TRAINER: Let them know and continue working with them. The more information you can give them on your progress, the easier it will be for them to alter your program as you go on.

IF YOU DON’T ENJOY WORKING WITH YOUR TRAINER: That’s okay too. Not all relationships end in marriages. Some first dates suck, and some trainers aren’t what you need. I think you can be honest with them and let them know that it’s not a good fit and you will not be continuing to work with them. Good trainers at this point will ask what they could have done better. Trainers who are simply after your money may guilt trip you or beg you to stick around. Try somebody new and keep the search going.

Remember: this is a lifelong quest, and you’re on the hunt for a great guide to help you on your journey. They won’t do the work for you, and they can’t work miracles. Have proper expectations, do what you’re told, and this could be the best investment you’ll make in your entire life!

Trainers in the Rebellion, what did I miss?

Those who have had experience working with Trainers, any wisdom to share from your experience?

-Steve

###

photo: wikimedia: high five, Gregg Wass: Trainer, Wikimedia: Spot, Wikimedia: stretchins

 

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Trail mix is meant for far more than long hikes. It’s meant for car rides, 3 p.m. hanger, long flights, and late-night snacking — just to name a few. It’s the ultimate snack for nearly any situation, which means it shouldn’t simply be a sad mix of raisins and peanuts. Toss in just one of these 15 additions to jazz up this well-loved snack.

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Let’s talk about the fajita effect. It’s the restaurant moment when a server swaggers by with a sizzling platter of fajitas and all heads turn to the sound and aroma of seasoned meat, peppers, and onions parading past the table. If you were smart enough to order that platter, you gloat as you pile warm tortillas with all the toppings and meat fresh from the skillet.

Recreating that exquisitely satisfying fajita effect at home is easier than you might think, and you can even make enough to share, thanks to the trusty, ever-versatile sheet pan.

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From Apartment Therapy → Clever Ways to Squeeze More Cookbooks into Your Collection

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When summer rolls around, watermelon should be in pretty much everything. Slushies, ice pops, salads, sangria — all benefit from the addition of this refreshing fruit. So it comes as no surprise that I fully endorse this watermelon salsa. With jicama, red onion, cilantro, and lime, it’s just the thing you need to elevate your Taco Tuesday plans.

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A whopping 97 percent of women and 68 percent of men report experiencing cravings for certain foods (1). Cravings are thought to be a combination of social, cultural, psychological, and physiological factors and are a major barrier to weight loss and optimal health for many individuals (2).

A recent body of evidence suggests that gut microbes might play a significant role in influencing cravings. Given that microbes co-evolved with us and constantly depend on the incoming dietary substrates that we provide for their own sustenance, it’s really no surprise that they are able to preferentially shape our eating preferences to improve their own chances of survival. In this article, I’ll discuss our current understanding of how microbes shape eating behavior and how you might use this information to combat cravings.

The gut-microbiota-brain axis

Most of us are well aware of the billions of neurons that make up the fatty, three-pound organ in our skull. But did you know that your gut also contains a dense network of neurons? This network, called the enteric nervous system, governs the physiological function of the gastrointestinal tract. In fact, this network is so robust that it is commonly referred to as the “second brain.”

The enteric nervous system is connected to the central nervous system (the brain and spinal cord) via the gut-brain axis. This is not a physical axis, but rather a term to collectively describe the interrelationship of the intestines and the brain. There are two ways in which they are connected. The first is the circulatory system. We have known for many years that hundreds of different hormonal, neuronal, and inflammation-related signals are constantly relayed between the gut and the brain via the bloodstream (3). Only recently, with the discovery of lymphatic vessels in the brain (4), have we come to understand that these gut-derived signals can likely enter the brain directly from the lymph as well.

The enteric nervous system is also connected directly to the brainstem via the vagus nerve. The vagus nerve acts as a superhighway for communication between the gut and the brain and is the longest nerve cell in the autonomic (unconsciously controlled) nervous system. Studies on the vagus nerve found that vagal blockade can lead to marked weight loss (5), while vagal stimulation triggers excessive eating in rats (6). In the next few sections, I’ll discuss the many other ways that microbes can influence eating behavior.

Craving a certain food? It could be your gut microbes are to blame.

Microbes have food preferences, too

Different microbes prefer different dietary substrates. While many microbes are “generalists” and can grow on a variety of substrates, they typically prefer one substrate over another, based on the amount of energy they can conserve during the process of breaking it down. Individual genera of bacteria have been shown to have these preferences. For example, Bacteroidetes has been shown to have a preference for particular fats; Prevotella grows best on a carbohydrate source; Bifidobacteria are able to outcompete others in the presence of dietary fiber (7, 8).  Other microbes are “specialists” and can only grow on a single nutrient source. Some microbes, such as Akkermansia muciniphila, do not depend on dietary substrates at all and instead thrive on the carbohydrate of the mucus layer secreted by host gut epithelial cells (9).

All of these microbes require a steady stream of substrates to grow and reproduce. Studies have shown that a low concentration of nutrients triggers increased virulence in many microbes as a survival mechanism. Virulence is the ability of a particular microbe to cause damage to the host. For many human-associated microbes, the production of virulence toxins is altered by the detection of simple sugars and other nutrients (10, 11).

Microbial neuroactives

When microbes break down (metabolize) dietary substrates, they produce by-products called metabolites. Microbial metabolites include many neuroactive agents (12, 13) that are small enough to penetrate the selectively permeable blood-brain barrier. Studies on chocolate cravings have found that even when eating identical diets, people who are “chocolate desiring” have different microbial breakdown products in their urine than people who are “chocolate indifferent” (14, 15).

So what are some of these metabolites? Short-chain fatty acids (SCFAs), breakdown products produced from the fermentation of dietary fiber in the GI tract, are able to modify the expression of genes in cells throughout the body, including brain cells. In particular, the SCFA butyrate has been shown to dampen the inflammatory response of microglia, the immune cells of the brain (16), and has profound effects on behavior and mood in mice (17).

Other microbially derived molecules are able to mimic hunger or satiety hormones. Your body normally secretes hormones like ghrelin (to stimulate your appetite) and peptide YY (to signal that you are full). Many gut bacteria are able to manufacture small peptides that mimic these hormones.

Interestingly, humans produce antibodies against these microbial hormone mimics in an effort to maintain the integrity of host signaling mechanisms. These antibodies, however, while meant to target microbial hormones, can also bind to mammalian hormones, effectively making them “auto-antibodies” (antibodies that react against one’s own body) (18). Microbes therefore can interfere with human appetite by either directly mimicking satiety and hunger hormones or indirectly inducing this autoimmune response.

Microbes produce neurotransmitters and influence neuroplasticity

Microbes may not have a nervous system, but they do produce neurotransmitters! More than 50 percent of your body’s dopamine and 90 percent of your body’s serotonin are produced in your gut, along with about 30 other neurotransmitters (19, 20). These molecules are critical for signaling between cells of the nervous system. Dopamine in the striatum and serotonin in the hypothalamus have both been shown to be involved in the regulation of eating behavior (21).

Microbes may also influence neuroplasticity, the ability of the brain to reorganize and create new neural pathways. This is particularly important since the formation of new connections between neurons may be necessary to reshape emotional eating behavior (22). One potent stimulator of neuroplasticity is brain-derived neurotrophic factor (BDNF). Studies have shown that mice lacking a gut microbiota (germ-free mice) have decreased levels of BDNF in the hippocampus, the learning and memory center of the brain. Hippocampal BDNF is also decreased in normal mice following antibiotic administration (23).  

Microbes shape host stress response, mood, and behavior

An increasing number of studies are showing connections between the gut microbiota, and stress, depression, and anxiety (24, 25). Poor mental health has long been associated with an increased likelihood to eat unhealthy foods (26). In 2004, a seminal experiment showed that germ-free mice raised in sterile conditions with no gut microbes had an exaggerated hypothalamic–pituitary–adrenal (HPA) axis response to stress (27). The effect was reversed by colonization with a single Bifidobacterium species. A similar 2013 study showed that germ-free mice had increased anxiety-like behavior, which was ameliorated by short-term colonization in adulthood.

Furthermore, a study published in 2012 found that germ-free mice prefer sweets and have a greater number of sweet taste receptors (28). While germ-free mice can tell us a lot about the role of microbes in mammalian physiology, they are certainly not very translatable to our own lives. At the end of this article, I’ll discuss a few human studies that have shown improvements in mood through interventions that manipulate the gut microbiota.

Microbial diversity may determine how susceptible you are to suggestions from your microbes

Microbial diversity may determine how easily host behavior can be manipulated.  Members of the microbiota constantly compete with one another over habitat and nutrients. A less diverse microbial population has fewer distinct microbial species and therefore likely has a few species with large population sizes. Researchers have hypothesized that species with large population sizes are able to use fewer resources for outcompeting other microbial species, leaving more resources available for manipulating the behavior of the host (29).

Interestingly, obese individuals tend to have lower microbial diversity than individuals of a healthy weight (30, 31). This may partially explain why people who are overweight tend to have more difficulty with food cravings. In other words, microbes could be a major barrier to weight loss.

Can manipulating the gut microbiota reduce cravings?

In this article, we discussed the connection between gut microbes and food cravings. Research on the oral microbiota may yet provide more links between microbes and our eating behavior. Functional and structural brain imaging alongside microbiota and metabolite analysis will be essential to improving our understanding of the microbiota–brain connection and its impact on human health and disease (32).

If you’re feeling powerless to the will of your microbes right about now, you should know that there are quite a few ways that we can manipulate them! The following list will help cultivate a healthy microbiota and may help you make better food choices.

  1. Probiotics
    Several strains of Bifidobacterium and Lactobacillus have been shown to improve anxiety- and depression-like behavior, which tend to alter eating behavior. In a randomized trial, women who ate a fermented milk product containing probiotics showed reduced activity in the insula and somatosensory cortices (emotional reactivity centers of the brain) in response to an emotional recognition task (33).
  2. Prebiotics
    Prebiotics are foods that selectively feed certain beneficial microbes over others. Prebiotics have been shown to increase BDNF (34), reduce waking cortisol and alter emotional processing (35), and induce satiety hormones (36). Try fermentable fiber in the form of foods like plantains, onions, garlic, and sweet potatoes, or consider supplementing with inulin or resistant starch.
  3. Focus on nutrient density
    A diverse microbiota tends to be a healthy microbiota. A diversified, nutrient-dense diet provides substrates to a wide range of microbes that can support your health and prevent any one population from gaining too much ground. Many people find that their cravings subside substantially after adopting a nutrient-dense diet for several months. This is likely mediated by a shift in their gut and oral microbiota.

Now it’s your turn! Did you know that gut microbes could influence food cravings? Have your cravings improved since adopting a nutrient-dense diet? Share your experience in the comments section.

 

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istock.com/gerenme

A whopping 97 percent of women and 68 percent of men report experiencing cravings for certain foods (1). Cravings are thought to be a combination of social, cultural, psychological, and physiological factors and are a major barrier to weight loss and optimal health for many individuals (2).

A recent body of evidence suggests that gut microbes might play a significant role in influencing cravings. Given that microbes co-evolved with us and constantly depend on the incoming dietary substrates that we provide for their own sustenance, it’s really no surprise that they are able to preferentially shape our eating preferences to improve their own chances of survival. In this article, I’ll discuss our current understanding of how microbes shape eating behavior and how you might use this information to combat cravings.

The gut-microbiota-brain axis

Most of us are well aware of the billions of neurons that make up the fatty, three-pound organ in our skull. But did you know that your gut also contains a dense network of neurons? This network, called the enteric nervous system, governs the physiological function of the gastrointestinal tract. In fact, this network is so robust that it is commonly referred to as the “second brain.”

The enteric nervous system is connected to the central nervous system (the brain and spinal cord) via the gut-brain axis. This is not a physical axis, but rather a term to collectively describe the interrelationship of the intestines and the brain. There are two ways in which they are connected. The first is the circulatory system. We have known for many years that hundreds of different hormonal, neuronal, and inflammation-related signals are constantly relayed between the gut and the brain via the bloodstream (3). Only recently, with the discovery of lymphatic vessels in the brain (4), have we come to understand that these gut-derived signals can likely enter the brain directly from the lymph as well.

The enteric nervous system is also connected directly to the brainstem via the vagus nerve. The vagus nerve acts as a superhighway for communication between the gut and the brain and is the longest nerve cell in the autonomic (unconsciously controlled) nervous system. Studies on the vagus nerve found that vagal blockade can lead to marked weight loss (5), while vagal stimulation triggers excessive eating in rats (6). In the next few sections, I’ll discuss the many other ways that microbes can influence eating behavior.

Craving a certain food? It could be your gut microbes are to blame.

Microbes have food preferences, too

Different microbes prefer different dietary substrates. While many microbes are “generalists” and can grow on a variety of substrates, they typically prefer one substrate over another, based on the amount of energy they can conserve during the process of breaking it down. Individual genera of bacteria have been shown to have these preferences. For example, Bacteroidetes has been shown to have a preference for particular fats; Prevotella grows best on a carbohydrate source; Bifidobacteria are able to outcompete others in the presence of dietary fiber (7, 8).  Other microbes are “specialists” and can only grow on a single nutrient source. Some microbes, such as Akkermansia muciniphila, do not depend on dietary substrates at all and instead thrive on the carbohydrate of the mucus layer secreted by host gut epithelial cells (9).

All of these microbes require a steady stream of substrates to grow and reproduce. Studies have shown that a low concentration of nutrients triggers increased virulence in many microbes as a survival mechanism. Virulence is the ability of a particular microbe to cause damage to the host. For many human-associated microbes, the production of virulence toxins is altered by the detection of simple sugars and other nutrients (10, 11).

Microbial neuroactives

When microbes break down (metabolize) dietary substrates, they produce by-products called metabolites. Microbial metabolites include many neuroactive agents (12, 13) that are small enough to penetrate the selectively permeable blood-brain barrier. Studies on chocolate cravings have found that even when eating identical diets, people who are “chocolate desiring” have different microbial breakdown products in their urine than people who are “chocolate indifferent” (14, 15).

So what are some of these metabolites? Short-chain fatty acids (SCFAs), breakdown products produced from the fermentation of dietary fiber in the GI tract, are able to modify the expression of genes in cells throughout the body, including brain cells. In particular, the SCFA butyrate has been shown to dampen the inflammatory response of microglia, the immune cells of the brain (16), and has profound effects on behavior and mood in mice (17).

Other microbially derived molecules are able to mimic hunger or satiety hormones. Your body normally secretes hormones like ghrelin (to stimulate your appetite) and peptide YY (to signal that you are full). Many gut bacteria are able to manufacture small peptides that mimic these hormones.

Interestingly, humans produce antibodies against these microbial hormone mimics in an effort to maintain the integrity of host signaling mechanisms. These antibodies, however, while meant to target microbial hormones, can also bind to mammalian hormones, effectively making them “auto-antibodies” (antibodies that react against one’s own body) (18). Microbes therefore can interfere with human appetite by either directly mimicking satiety and hunger hormones or indirectly inducing this autoimmune response.

Microbes produce neurotransmitters and influence neuroplasticity

Microbes may not have a nervous system, but they do produce neurotransmitters! More than 50 percent of your body’s dopamine and 90 percent of your body’s serotonin are produced in your gut, along with about 30 other neurotransmitters (19, 20). These molecules are critical for signaling between cells of the nervous system. Dopamine in the striatum and serotonin in the hypothalamus have both been shown to be involved in the regulation of eating behavior (21).

Microbes may also influence neuroplasticity, the ability of the brain to reorganize and create new neural pathways. This is particularly important since the formation of new connections between neurons may be necessary to reshape emotional eating behavior (22). One potent stimulator of neuroplasticity is brain-derived neurotrophic factor (BDNF). Studies have shown that mice lacking a gut microbiota (germ-free mice) have decreased levels of BDNF in the hippocampus, the learning and memory center of the brain. Hippocampal BDNF is also decreased in normal mice following antibiotic administration (23).  

Microbes shape host stress response, mood, and behavior

An increasing number of studies are showing connections between the gut microbiota, and stress, depression, and anxiety (24, 25). Poor mental health has long been associated with an increased likelihood to eat unhealthy foods (26). In 2004, a seminal experiment showed that germ-free mice raised in sterile conditions with no gut microbes had an exaggerated hypothalamic–pituitary–adrenal (HPA) axis response to stress (27). The effect was reversed by colonization with a single Bifidobacterium species. A similar 2013 study showed that germ-free mice had increased anxiety-like behavior, which was ameliorated by short-term colonization in adulthood.

Furthermore, a study published in 2012 found that germ-free mice prefer sweets and have a greater number of sweet taste receptors (28). While germ-free mice can tell us a lot about the role of microbes in mammalian physiology, they are certainly not very translatable to our own lives. At the end of this article, I’ll discuss a few human studies that have shown improvements in mood through interventions that manipulate the gut microbiota.

Microbial diversity may determine how susceptible you are to suggestions from your microbes

Microbial diversity may determine how easily host behavior can be manipulated.  Members of the microbiota constantly compete with one another over habitat and nutrients. A less diverse microbial population has fewer distinct microbial species and therefore likely has a few species with large population sizes. Researchers have hypothesized that species with large population sizes are able to use fewer resources for outcompeting other microbial species, leaving more resources available for manipulating the behavior of the host (29).

Interestingly, obese individuals tend to have lower microbial diversity than individuals of a healthy weight (30, 31). This may partially explain why people who are overweight tend to have more difficulty with food cravings. In other words, microbes could be a major barrier to weight loss.

Can manipulating the gut microbiota reduce cravings?

In this article, we discussed the connection between gut microbes and food cravings. Research on the oral microbiota may yet provide more links between microbes and our eating behavior. Functional and structural brain imaging alongside microbiota and metabolite analysis will be essential to improving our understanding of the microbiota–brain connection and its impact on human health and disease (32).

If you’re feeling powerless to the will of your microbes right about now, you should know that there are quite a few ways that we can manipulate them! The following list will help cultivate a healthy microbiota and may help you make better food choices.

  1. Probiotics
    Several strains of Bifidobacterium and Lactobacillus have been shown to improve anxiety- and depression-like behavior, which tend to alter eating behavior. In a randomized trial, women who ate a fermented milk product containing probiotics showed reduced activity in the insula and somatosensory cortices (emotional reactivity centers of the brain) in response to an emotional recognition task (33).
  2. Prebiotics
    Prebiotics are foods that selectively feed certain beneficial microbes over others. Prebiotics have been shown to increase BDNF (34), reduce waking cortisol and alter emotional processing (35), and induce satiety hormones (36). Try fermentable fiber in the form of foods like plantains, onions, garlic, and sweet potatoes, or consider supplementing with inulin or resistant starch.
  3. Focus on nutrient density
    A diverse microbiota tends to be a healthy microbiota. A diversified, nutrient-dense diet provides substrates to a wide range of microbes that can support your health and prevent any one population from gaining too much ground. Many people find that their cravings subside substantially after adopting a nutrient-dense diet for several months. This is likely mediated by a shift in their gut and oral microbiota.

Now it’s your turn! Did you know that gut microbes could influence food cravings? Have your cravings improved since adopting a nutrient-dense diet? Share your experience in the comments section.

 

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Why spend hours in the kitchen when you can be out enjoying summertime fun?

Summer has arrived and the sun beckons us outdoors, often leaving meals as a secondary thought while enjoying patio time or outdoor training sessions. Long training days require easy meals to power through workouts and support your performance.

 

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