athlete body composition

7 Factors that Influence Adult Athlete Body Composition

Adult athlete body composition is influenced by physiological and emotional factors.   Having an understanding of the factors that impact body fat and lean muscle mass can help athletes outline a personalized game plan.  This game plan helps adult athletes set realistic goals, and outlines the approach for achieving desired changes in body composition.   These changes, such as lowering body fat or increasing muscle mass, may result in improved athletic performance.   Here are the 7 factors that influence adult athlete body composition.


Aging is a natural process that induces physiological changes in the body.   As humans age, their resting metabolic rate decreases which alters the rate at which they make and use ATP.  They also will begin to notice a decline in lean muscle mass at the age f 30, especially in the form of Type II or fast-twitch muscle fibers.   Bone mineral density also naturally decreases with age which can cause fat-free mass (the weight of muscles, bones and organs) to decline.   

The aging process is inevitable, but it can be delayed through proper nutrition, regular physical activity, consistent movement and effective stress management.  


Sex hormones, mainly estrogen and testosterone, determine body shape and body type during adolescent years.  For adults,  hormones also play a huge role in how much fat is stored and where it is stored.  Testosterone plays a significant role in muscle hypertrophy (aka building of muscle).  As adults age, their hormone levels change which is why it is important to ensure that hormones remain balanced as athletes get older.  Hormone imbalance can lead to fat being deposited on the stomach and can make it difficult to lose excess body fat.   This article outlines the relationship between sex hormones, body composition and aging.  

Growth hormone (GH) is another hormone that has a profound impact on body composition in adult athletes.   This hormone, produced by the pituitary gland, is responsible for growth during childhood.  In adults, GH helps to maintain the growth and regeneration of tissues and organs and maintains body structure and metabolism.   In men, GH and testosterone decline with age which is often why growth hormone and testosterone supplementation are used to increase lean body mass, reduce fat mass and improve muscle strength of older men. 

Also ReadCommon Endocrine Disrupting Chemicals

Adequate levels of GH boost muscle growth, strength, recovery and performance in both males and females.  Lower levels are GH have been found to be associated with obesity and poor health.  Instead of reaching for the supplements, I would encourage adult athletes to take a look at their health first.  GH levels can be optimized by high-intensity exercise, strength training, intermittent fasting, reducing sugar intake, and making sure you’re getting enough good quality sleep. 


When stress is perceived, the stress response is turned on by triggering the release of cortisol from the adrenal glands.   Cortisol is important for helping to control blood sugar levels, regulating metabolism, reducing inflammation, balancing fluid, and controlling blood pressure.  This hormone is crucial for the protection of overall health and well-being, and for helping the body survive when faced with a threat. 

Cortisol is an important hormone for the body, but too much of it can cause problems.  High cortisol levels lead to excess body fat being stored in the body and also impact the balance of sex hormones in both males and females.  In females, high cortisol contributes to changes in libido and irregular menstrual cycles.  In men, high cortisol interferes with the production of testosterone which can lead to poor recovery, fatigue, breakdown of muscle tissue, and increased fat around the organs.   

Some stress is beneficial for human health and athletic performance, but chronic stress can lead to fat gain, muscle loss, or both. 


When it comes to food, the quality, quantity, type and timing all influence body composition.  The nutrients that we consume through our food are all utilized effectively and efficiently by our bodies.  These substances in our food are broken apart through digestion and used in a variety of ways.  Nutrients create our form (cells, tissues, and organs), or help with some biological function (enzymes, hormones, transport, energy, neurotransmitters).   

QUALITY: The five categories of nutrients that are most important for optimum form and function are: 

When it comes to food quality, those foods that contain nutrients from 1 or more of these categories are the ones that will support our form and function.  Other substances in food, such as artificial sweeteners, food additives, flavor enhancers, artificial colors, and highly-processed ingredients interfere with our form and function. 

Also Read5 Pillars of Nutrition for Athletes

QUANTITY: The human body is incredibly resourceful when it comes to nutrients.  Whatever is not used immediately for form or function, is stored for later.  When it comes to body composition, quantity (i.e. number of calories consumed) is just one piece of the puzzle.   In order to change body composition through nutrition, quality, type and timing must also be considered.

TYPE: The type of calories consumed, particularly the macronutrients including proteins, carbohydrates and fat, are important to consider when changing body composition with the help of dietary changes.   If you consume too many carbohydrates or fats, you risk the excess energy being stored on the body as fat.  If you don’t consume enough protein, you risk losing precious muscle mass and/or will be unable to grow more.  

TIMING: As athletes, the timing of nutrients is important for performance but also influences body composition.  What, how much and you consume the food before, during and after activity plays a big role in influencing body composition.  If you’re not fueling properly before or not recovering properly after activity, your body may steal protein from your muscles to use it for other purposes such as energy or building hormones.   

Gut health

The microorganisms in your gut and the permeability of your intestinal walls can influence body composition.  There are certain microorganisms, or microbes, in your gut that help to maintain healthy body weight, support the immune system and regulate metabolism.  These microbes affect how foods are digested and contribute to the release of chemicals that make us feel full.  The type of microbes is important, but the balance or diversity of microbes is important, too.   An unhealthy diet can cause these beneficial microbes to die off and therefore will interfere with digestion, absorption of nutrients, satiety signaling and normal metabolism.   

Also Read5 Daily Habits to Build a Strong Immune System

The permeability of the intestinal walls is also important because the size of the holes determines the type of substances that get through to the bloodstream.  If the holes are too small, not enough essential nutrients will pass through.  If the holes are too large, this may result in harmful and/or foreign substances passing through.  When the holes are too large, this is a condition called “leaky gut” which can trigger an immune response.  This immune response can show up in a variety of ways from inflammation and intestinal bloating, to brain fog and skin rashes. 

Physical activity

Body composition is heavily influenced by the way that the body moves and how much energy is expended.  Different types of training determine whether the body will utilize excess body fat for energy or encourage hypertrophy (muscle growth).   The total energy expenditure and the type of energy system – phosphagen, aerobic or anaerobic – that is utilized during training is also important for whether the body turns to body fat for energy or supports muscle growth. 

Energy expenditure is influenced by frequency (how often), intensity (how difficult), and duration (how long) of activity.  A strategic energy expenditure that burns calories but has enough nutrients available to support muscle maintenance or growth, will result in the shedding of excess body fat.  


In order to reach body composition goals, it will require the ability to stay consistent and motivated and to remain patient enough to see results.  The mind can hold athletes back from reaching any performance goal, and that includes goals related to body composition.  If an athlete doesn’t believe in their ability to achieve a goal, they aren’t likely to follow through with the actions that it takes to do so.   

Also ReadTop 10 Daily Habits to Develop a Growth Mindset

If an athlete struggles with discipline, their ability to remain consistent and motivated will suffer.  This article discusses the importance of having a strong mindset in order to change body composition.  

Want to learn how to lose body fat, gain muscle or both?

In my Body Composition for Adult Athletes Workshop,  I’ll teach you 4 shifts you need to make in order to change your muscle to fat ratio for the benefit of your performance.   It also includes a handy workbook. Click on the below to learn more about this fantastic low-cost (and high value!) offer. 

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