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Evidence based

Evidence Based

This article is based on scientific evidence, written by experts and fact checked by experts.

Our team of licensed nutritionists and dietitians strive to be objective, unbiased, honest and to present both sides of the argument.

This article contains scientific references. The numbers in the parentheses (1, 2, 3) are clickable links to peer-reviewed scientific papers.

Improve Your Body Composition in 3 Steps

Written by on March 26, 2024

A Proven Blueprint to Help You Lose Fat and Gain Muscle

Key Takeaways:

  • Body composition refers to the amounts of fat, muscle, bone, and water you carry in your body.
  • Having more muscle mass tends to reduce your risk of chronic disease and sarcopenia as you age, whereas excess fat can have the opposite effect.
  • The gut-muscle connection likely plays an important role in regulating your metabolism.
  • Gut-directed strategies play a crucial and overlooked step in body composition.
  • While exercise is a tried-and-true way to improve body composition, certain dietary patterns and supplements can give an important edge over exercise alone.

 

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 a gut-muscle connection that helps to regulate your 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 for improving your own body composition. First, let me share an overview of the steps you can take to start adding muscle and losing fat. 

3-Step Body Composition Guide Overview

I’ll go into more detail about each of the steps in this process later on, but here’s a quick overview of how to build a foundation that supports healthy body composition: 

Step Description Implementation Tips
1 Diet and Exercise
  • Anti-inflammatory diet with a minimum of 1.3 grams of protein per kilogram of body weight
  • 30 minutes of moderate-to-high-intensity cardiovascular training 3 days each week
  • 3 or more days of full-body resistance training each week
2 Dietary Supplements
  • 3–5 grams of creatine per day
  • Whey protein (or plant-based protein) powder if dietary protein intake is insufficient
  • A high-quality probiotic that contains all 3 categories of probiotics
3 Intermittent Fasting
  • 12-hour overnight fasting or other fasting method that works for you

As you can see, it’s important to start with diet and exercise first and then move on to the other steps once you’ve got those two dialed in. Now, let me get into a little background on body composition.

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. 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 less chance of sarcopenia-related complications as you age [3, 4]. 

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. Where we’ve tended to focus much of our efforts on weight loss to reduce excess body fat, we’ve ended up ignoring 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 our diets and practicing resistance training are the most impactful strategies for improving body composition, there is a role for your 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 your 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. 

Your gut health impacts practically every system in your body, and this seems to be the case for your muscles too. While research is still ongoing, a harmonious cycle may exist between your gut and your muscles, where information from your gut impacts your muscles, and information from your muscles impacts your gut [1, 5, 6].

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

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

In general, more gut microbial diversity tends to equal better health [1]. Your good gut bugs produce SCFAs, like butyrate, to support immune system function, reduce inflammation, and provide you and your muscles with energy [1, 5, 6]. It’s not super important that you remember all of these details. The take-home message here is that when you zoom out, the gut-muscle connection may be an important consideration when it comes to your body composition.

Since more gut microbial diversity may improve muscle health and metabolism, this gives us a good target. Diet, physical activity, and probiotics can all increase the diversity of your beneficial gut bugs, which may translate into improved body composition. So let’s take a look at the research on probiotics and body composition specifically. 

Probiotics and Body Composition

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

One meta-analysis found people with obesity or those who were overweight had a slight improvement in their body composition (specifically less fat tissue) after taking single or multi-strain probiotics for 8 weeks [7]. While this isn’t the wow factor you’re probably hoping for, it highlights how probiotics may be used in conjunction with other positive measures to help support a healthier body composition. 

Moving on to athletes, a 3-month randomized controlled trial found 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 [8].

Another trial of healthy adults (non-athletes) randomized participants 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 the probiotics had significantly better performance, less fatigue, and healthier changes in body composition (more muscle and less fat) compared to the placebo group. It’s interesting to note that both probiotic groups had improvement, but the high-dose probiotic group had better results when compared to the low-dose group [9].

Finally, a 2022 randomized controlled trial of older people with sarcopenia 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 for sure to what extent the probiotic was responsible for the improvements [10].  

Summing this up, probiotics may exert their benefits on body composition by improving the gut microbial community. A healthy balance of microbes in the GI tract may 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 [8].

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 for improving body composition I promised earlier.

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. So, 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 [11].  

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 your body composition requires you to lay a healthy foundation with diet and exercise first. 

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 [11, 12]. One 2012 randomized controlled trial found people who ate 15–25% of their daily calories in 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 [11].

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 [13, 14]. 

So, how much protein do you need? One 2020 meta-analysis looking at 105 randomized controlled trials found increasing your 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 [15]. To convert kilograms to pounds, divide your weight in pounds by 2.2. So, for a 175-pound person, divide 175 by 2.2 to get 79.5 kilograms of body weight. Multiply 79.5 kg by 1.3 grams of protein, and you 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 [6]. 

If you’re not currently doing any type of physical activity, I want you to just get moving. If you’re able to, start off with walking as much and as often as you can. Once you get that baseline under your belt, then 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, you’ll likely get the most bang for your buck when it comes to body composition by prioritizing resistance training. Resistance training is the best way we know of to increase your muscle size and the amount of lean body mass you have, which both help to boost your metabolism [16, 17]. 

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 [16]
  • Resistance training induces more muscle gain than a combination of resistance training and high-intensity interval training (not that HIIT is a bad thing) [17]
  • You don’t need to push yourself to failure during training to gain muscle mass from resistance training [18]

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 being said, you don’t need a lot of fancy equipment to get started with resistance training. You can 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 your way up to 3 resistance training sessions per week. 


Okay, so once you’ve laid the foundation with diet and exercise, you can move on to step 2 and consider adding dietary supplements.

Step 2: Dietary Supplements

The dietary supplement industry is big business, and there are a lot of supplements targeted toward body composition. I’m not a fan of loading up on supplements, but there are a few science-based options like creatine, protein powder, and probiotics for you to consider. Here’s a table summarizing the research and how to add them to your routine:

Dietary Supplement Research Findings Recommended Dose
Creatine
  • Increases muscle strength [19, 20]
  • Enhances muscle growth [21]
  • Improves body composition, especially in younger males [22]
  • Improves strength, functional capacity, and lean mass in older adults [23, 24, 25]
  • Best results when combined with resistance training.
  • Start with a loading phase by taking 5 grams of creatine monohydrate 4 times per day (total daily dose of 20 grams) for 5-7 days. After the loading phase is complete, take a maintenance dose of 3-5 grams per day (larger athletes may need 5-10 g/day) [26]
Protein Powder
  • Whey protein with resistance training significantly improves lean mass, fat mass, and muscular strength in healthy people, especially those under the age of 40 [27]
  • Whey protein appears to modestly increase lean mass without changing fat mass in women, especially when combined with a calorie-restricted diet [28]
  • Whey protein significantly increases muscle mass without changing fat mass, overall body mass, or body fat percentage in adults. Soy protein had no effect [29]
  • If you’re falling short on dietary protein, consider a high-quality protein supplement (whey or plant-based) with at least 20 grams of protein per serving to augment your intake 
Probiotics
  • Single and multi-strain probiotics reduce body weight, waist circumference, and fat mass to a small extent [7]
  • Single and multi-strain probiotics improve body composition in athletes [30]
  • Multi-strain probiotics improve muscle mass and lean body mass in men and reduce fat mass in women [8]
  • High-dose probiotics reduce fat mass and increase muscle mass in healthy people [9]
  • Choose a high-quality probiotic that contains all 3 categories of probiotics (Lactobacillus/Bifidobacterium blend, Saccharomyces boulardii, and soil-based)

As you can see, these are all well-researched dietary supplements with some body composition benefits. However, you’ll notice that 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 likely won’t significantly improve your body composition on their own.

Once you’ve worked your way through steps 1 and 2, you may want to check out step 3 and 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 [31]. 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 [32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45]. IF may also improve body composition and lean muscle mass, as well as support endurance, strength, and performance [46, 47, 48, 49, 50, 51].

While IF doesn’t appear to impact your metabolic rate directly, it may improve your body composition and enhance weight loss [52, 53]. One randomized controlled trial found men who ate during an 8-hour window and practiced resistance training had increased fat loss while they preserved muscle mass [52]. As one literature review explained, part of these effects may be due to the ability of fasting to help your body switch from burning glucose to fat, meaning you’re breaking down stored fat into ketones to provide energy to the rest of your body [53]. 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 the different IF methods and how they’re implemented [31]:

Body composition
  • Time-restricted eating—set fasting and eating “windows,” followed between 1–7 times a week. For example, you could choose to practice 12-hour overnight fasting, meaning stopping food intake after dinner and then not eating again for 12 hours. 
  • The twice-a-week (5:2) method—restricts your 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, non-processed foods on non-fasting days

I want to point out here that fasting isn’t a requirement for improving your body composition. Everyone reacts differently, so it’s important to listen to your body. If fasting feels good to you, you can incorporate it into your routine. If you feel worse when you fast, there’s no need to force yourself to do it. 

Improve Your Body Composition with Diet, Exercise, and Probiotics

Body composition refers to the amounts of muscle, fat, bone, and water in your 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 your body. Body composition assessment, using one of various methods, is the gold standard for determining your muscle-to-fat ratio, which is much more helpful for assessing your overall health risk.

Having more muscle and less fat tends to reduce your chance of chronic disease and enhance your quality of life as you get older. While we know improving body composition takes diet and exercise, optimizing your gut health and gut microbial diversity may also be an important consideration. Research is ongoing, but suggests we have a gut-muscle connection where myokines released from our muscles support our gut in releasing GLP-1, and the SCFAs produced by our gut bacteria help our muscles regulate how they use energy. 

Probiotics are well-studied and have a variety of benefits, including possibly increasing muscle mass and improving overall body composition. You’ll have the most success, though, by focusing on a higher protein anti-inflammatory diet and resistance training first, then adding in helpful dietary supplements like probiotics and creatine, and possibly intermittent fasting. 

If you need help in optimizing your gut 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 patients 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.

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.
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