A Blueprint for Losing Fat and Gaining Muscle

• Body Composition 101|
• The Gut-Muscle Connection|
• Probiotics & Body Composition|
• Guide to Improving Body Composition|
• Improve Body Composition with Diet, Exercise, and Probiotics|

Most of us probably already know that diet and exercise are foundational for managing the amount of body fat and muscle we carry. But did you know that harnessing the power of the bacteria in your gut may also be important for improving your body composition?  

This may sound a little far-fetched, but current science-based theories suggest there’s a gut-muscle connection that helps to regulate metabolism and the types of bacteria that live in your gut [1]. This is really cool because it applies whether you’re an athlete looking for an edge, a weekend warrior, or someone who’s just hoping to reduce your body fat and increase muscle mass. 

In this article, I’ll define what body composition is and why it needs to be on your radar. I’ll also dig into what we know about the gut-muscle connection and give you a step-by-step guide to get you on the right path toward improving your own body composition. First, let me share an overview of the steps you can take to start adding muscle and losing fat.

Body Composition 101

Simply said, body composition refers to the relative percentages of fat, bone, muscle (lean tissue), and body water that you’re made of. A body composition analysis can be accomplished with several methods, including:

• Hydrostatic weighing (underwater weighing)
• Skinfold thickness assessment (skinfold measurements with calipers)
• The BOD POD (using air displacement plethysmography)
• Bioelectrical impedance
• DXA (DEXA scan or dual energy x-ray absorptiometry)

You may be wondering why you’d want to know how much total body fat and fat-free mass you have. This information can provide a lot of insight about your health risk and how you’ll fare as you age. 

When it comes to your overall health, you can probably guess that it’s best to have a pretty high ratio of muscle to fat. This is not to say that body fat is bad; you need a certain amount of fat for important functions like:

• Vitamin absorption
• Temperature regulation
• Hormone production and regulation
• Exercise fueling
• Nerve cell signaling
• Cell structure
• Organ protection

That said, though, having a higher body fat percentage is associated with an increased risk of chronic diseases like type-2 diabetes, heart disease, cancer, and high blood pressure [2]. Having higher muscle mass, on the other hand, is associated with reduced health risks and a lower chance of muscle wasting and related complications as we age [3]. 

I had an excellent discussion about this on the podcast with Dr. Gabriel Lyon, a muscle-centric functional medicine practitioner. I really appreciate her perspective on body composition: 

Our cultural tendency  to focus our weight-loss efforts on reducing excess body fat has sidelined the extreme importance of building and maintaining skeletal muscle mass. More muscle means healthier aging, better metabolic health, and overall improved health outcomes.  

While we know improving the diet and practicing resistance training are the most impactful strategies for improving body composition, there is a role for gut bugs in this equation, too. In the intro, I hinted about the gut-muscle connection, so let’s unpack that and look at how gut health contributes to body composition.

The Gut-Muscle Connection

You’ve likely heard of the gut-brain connection or maybe even the gut-thyroid connection, but we may also have a gut-muscle connection. 

Gut health impacts practically every system in the body, and this seems to be the case for muscle health, too. Research is uncovering a harmonious cycle that may exist between the gut and muscles, in which information from the gut impacts the muscles, and information from the muscles impacts the gut [1, 4, 5].

For gut geeks like me, here’s a closer look at the relationship between the gut and the muscles [1]:

• Muscle-to-Gut—When muscles contract during exercise, they release myokines (anti-inflammatory signaling molecules). Some myokines may help the gut release GLP-1, an important hormone for healthy metabolism.
• Gut-to-Muscle—Short-chain fatty acids (SCFAs) made by gut bacteria can help regulate how the muscles use energy and may improve how the body uses glucose for fuel.

In general, more gut microbial diversity tends to equal better health [1]. Certain good gut bugs produce SCFAs, like butyrate, to support immune system function, reduce inflammation, and provide us and our muscles with energy [1, 4, 5]. 

It’s not important to remember all of these details. The take-home message is that the gut-muscle connection may be important to consider when it comes to body composition.

Since more gut microbial diversity may improve muscle health and metabolism, targeting gut health makes sense. Diet, physical activity, and probiotics can all increase the diversity of our beneficial gut bugs, which may translate to improved body composition. So, let’s take a look at the research on how probiotics affect body composition. 

Probiotics and Body Composition

Probiotics probably come to mind when you think about improving GI-related symptoms like reflux, bloating, and constipation. But several studies have found probiotics can also help improve body composition in various groups, from athletes to older people.

One meta-analysis found that people who carried excess weight had a slight improvement in their body composition (less fat tissue) after taking single or multi-strain probiotics for 8 weeks [6]. 

While this isn’t the wow factor you’re probably hoping for, it highlights how probiotics may boost the effects of other measures to support a healthier body composition. 

Moving on to athletes, a 3-month randomized controlled trial found that men who took multi-strain probiotics had significantly improved lean body mass and muscle mass. Meanwhile, women taking the multi-strain probiotics only leaned toward having less fat. These gender differences may have been related to the type and intensity of their exercise, dietary differences, and the presence of GI disorders [7].

Another trial randomized healthy adults (non-athletes) to take a placebo, a low-dose probiotic, or a high-dose probiotic for 6 weeks. At the end of the study, people who took probiotics (especially the high-dose) had better performance, less fatigue, and healthier changes in body composition (more muscle and less fat) than the placebo group [8].

Finally, a randomized controlled trial of older people with sarcopenia (muscle loss) found taking a supplement containing omega-3 fatty acids, leucine (an amino acid), and Lactobacillus paracasei (a probiotic) for 8 weeks significantly improved lean body mass, abdominal fat, as well as physical performance and strength when compared to a placebo. Since this study used a combination supplement, we can’t say to what extent the probiotic was responsible for the improvements [9].  

In summary, probiotics may benefit body composition by improving the gut microbial community, which may positively impact muscles through the gut-muscle connection. A healthy balance of microbes in the GI tract may also improve your ability to absorb nutrients, enhance your exercise duration and effectiveness, and improve your recovery from training, all of which can help improve body composition [7].

I would love nothing more than to tell you that taking a probiotic without changing your diet and lifestyle can optimize your body composition. Probiotics may help to move the needle in the right direction, but for optimal results, you need a comprehensive plan. 

So, let’s get into the step-by-step guide I give my clients seeking to improve their body composition.

Improving Body Composition: A Step-By-Step Guide

Body composition is truly an important concept for everyone, regardless of how much you weigh. Let me elaborate by saying that body composition is independent of the number on the scale. In other words, being at a healthy weight doesn’t necessarily give you a free pass. 

You could have a “normal” body mass index (BMI) and still have an unhealthy muscle-to-fat ratio, which will increase your risk of chronic disease and sarcopenia. Likewise, since muscle weighs more than fat, you could be at a higher weight, have what’s considered to be an “unhealthy” BMI, and yet still have an excellent muscle-to-fat ratio [10].  

So, what’s the best way to optimize body composition? Unfortunately, there’s no silver bullet, but practicing science-based strategies consistently over time will get you there. Here’s a step-by-step guide to get you started.

Step 1: Diet and Exercise

I know I sound like a broken record, but improving body composition requires a healthy foundation of diet and exercise. 

Diet for Body Composition

We’re all unique and have different needs and preferences, so I’m not in any particular dietary camp. 

Most anti-inflammatory diets (like Paleo and Mediterranean) will likely help you meet your body composition goals as long as you’re prioritizing protein. 

This may be due in part to the ability of protein to increase your resting metabolic rate and promote muscle growth instead of fat building [10, 11]. One randomized controlled trial found that people who ate 15–25% of their daily calories as protein gained up to 8 pounds of lean mass and had significantly greater increases in their metabolic rate when compared to people who consumed only 5% of their daily calories in protein [10].

Additionally, research suggests the current recommended dietary allowance (RDA) for protein is far too low, especially if we’re active and as we get older. Observational research shows that higher protein intake is associated with better physical performance and muscle strength, and a reduced risk of hip fracture in older people [12, 13]. 

So, how much protein do you need? One meta-analysis found that increasing daily protein intake to at least 1.3 grams per kilogram of body weight per day can help increase or maintain your lean body mass [14]. 

To convert kilograms to pounds, divide your weight in pounds by 2.2. So, a 175-pound person would divide 175 by 2.2 to get 79.5 kilograms of body weight. Multiply 79.5 kg by 1.3 grams of protein, and they would need a minimum of 103 grams of protein each day. 

Exercise for Body Composition

We all know exercise is good for us. Moving our bodies can help to keep our weight under control, improve our sleep and mood, and keep our hearts healthy. But moderate-to-high intensity exercise lasting for about 30 minutes may also be good for the gut microbiome, which may help optimize the gut-muscle connection and translate into better body composition [5]. 

For my clients who don’t do any type of physical activity, I recommend that they just get moving. If they can, I suggest they start off with walking as much and as often as they can. Once they get that baseline under their belt, then we move on to more formal cardiovascular and resistance training exercises. 

While cardiovascular exercise (running, fast walking, swimming, and cycling) is critical for overall health and gut function, resistance training may offer the most bang for the buck. 

Resistance training is the best way we know of to increase muscle size and lean body mass, which both help to boost metabolism [15, 16]. 

Here’s a look at what several meta-analyses have found regarding resistance training and body composition:

• Compared to no exercise, resistance training of any kind improves strength and muscle gain [15].
• Resistance training induces more muscle gain than a combination of resistance training and high-intensity interval training (not that HIIT is a bad thing) [16].
• We don’t need to push ourselves to failure during training to gain muscle mass from resistance training [17].

If you’re new to resistance training, you may want to work with an exercise professional who can develop a personalized plan to get you started safely. That said, you don’t need a lot of fancy equipment to get started with resistance training. 

I often recommend that my clients begin at home with some inexpensive light hand weights or resistance bands and free online videos. The point is to just get started and progress to using higher amounts of weight and more intensity as time goes on, and work up to 3 resistance training sessions per week. 

Once the foundation of diet and exercise are in place, we move on to step 2: considering dietary supplements.

Step 2: Dietary Supplements

The dietary supplement industry is big business, and there are a lot of supplements targeting body composition. I’m not a fan of loading up on supplements, but a few science-based options like creatine, protein powder, and probiotics are worth considering. Here’s a table summarizing the research on these supplements and how they might fit in a routine:

As you can see, these are all well-researched dietary supplements with some body composition benefits. However, obtaining the maximum benefit requires laying the foundation of a higher-protein anti-inflammatory diet and exercise first. 

Using these supplements on their own may provide some small benefits, but they likely won’t go far toward improving body composition.

Once my clients have worked through steps 1 and 2, we check out step 3 to see if they’d like to try intermittent fasting.

Step 3: Intermittent Fasting

Intermittent fasting (IF) is the practice of repeatedly alternating between periods of calorie restriction and normal unrestricted eating [30]. In other words, you cycle between periods of eating and periods of avoiding or limiting food. 

A large body of high-quality evidence has found that intermittent fasting can benefit metabolic health, heart health, and weight loss, perhaps especially in people with metabolic syndrome [31, 32, 33, 34, 35]. IF may also improve body composition and lean muscle mass [36], as well as support endurance, strength, and performance [37, 38, 39, 40].

While IF doesn’t appear to impact the metabolic rate directly, it may improve body composition and enhance weight loss [41, 42]. For example, a randomized controlled trial found that men who ate during an 8-hour window and practiced resistance training had increased fat loss while keeping their muscle mass [41]. 

These effects may occur in part because fasting can help the body switch from burning glucose to fat. In other words, IF breaks down stored fat into ketones to provide energy to the rest of your body [42]. 

When you think about fasting, you may assume it always means avoiding food intake during the daylight hours, but there are many different ways to incorporate IF. Here’s an overview of different IF methods and how they’re implemented [30]:

• Time-restricted eating—Set fasting and eating “windows,” followed between 1–7 times a week. For example, fasting overnight for 14 hours allows a 10-hour eating window. 
• The twice-a-week (5:2) method—Restricting daily calories (often to 500) for 2 non-consecutive days a week and eating normal, healthy whole (not processed) foods the other 5 days of the week
• Modified alternate-day fasting—A modified fast every other day or 2 nonconsecutive days of the week
• The 24-hour fast (eat: stop: eat) method—Fasting (consuming only water) for 24 hours once or twice a week and eating normal, healthy, whole foods on non-fasting days

I want to point out here that fasting isn’t a requirement for improving body composition. Everyone reacts to IF differently, so it’s important to listen to your body. 

When fasting feels good to my clients, I help them incorporate it into their routine. But if they feel worse when they fast, there’s no need to force it. 

Improve Body Composition with Diet, Exercise, and Probiotics

Body composition refers to the amounts of muscle, fat, bone, and water in the body. In clinical practice, we often use weight as a measure of whole-body health. But this gets tricky because the number on the scale doesn’t give us any real information about what’s going on inside the body. Body composition assessment is the gold standard for determining the muscle-to-fat ratio, which is much more helpful for assessing overall health risk.

Having more muscle and less fat tends to reduce the chance of chronic disease and enhance quality of life as we get older. While we know improving body composition takes diet and exercise, optimizing gut health and gut microbial diversity may also play a role. Research is ongoing, but it suggests we have a gut-muscle connection, or a bi-directional relationship between the two that benefits both. 

Probiotics are well-studied and may help increase muscle mass and improve overall body composition. I tend to see the most success, though, when people focus on a higher protein anti-inflammatory diet and resistance training first, and then add in helpful dietary supplements and possibly intermittent fasting. 

If you need help in optimizing your gut (and muscular) health, check out my book, Healthy Gut, Healthy You, for a step-by-step gut-healing guide, or contact us for an appointment at the Ruscio Institute for Functional Health.

The Ruscio Institute has developed a range of high-quality formulations to help our clients and audience. If you’re interested in learning more about these products, please click here. Note that there are many other options available, and we encourage you to research which products may be right for you. The information on DrRuscio.com is for educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment.

Dr. Michael Ruscio is a DC, Naturopathic Practitioner, researcher, and clinician. He serves as an Adjunct Professor at the University of Bridgeport and has published numerous papers in scientific journals as well as the book Healthy Gut, Healthy You. He also founded the Ruscio Institute of Functional Health, where he helps patients with a wide range of GI conditions and serves as the Head of Research.