7 factors that affect body composition

Sue Heikkinen, MS, RDN, CDCES, BC-ADM, ACE-PT - Registered Dietitian Nutritionist and Certified Diabetes Care and Education Specialist

You know that body fat percentage is a better marker of health than weight alone. Learn the factors that affect body composition, including a few that are, sadly, not in your control.

Body fat and the 7 main factors that affect body composition

Despite the negative associations, body fat is essential-we need a certain amount for proper hormone function and to protect our organs and provide insulation. Yet a higher percentage of body fat can come with health risks. Understand your total body composition and the factors that affect it so you can take steps to stay healthy.

The factors to watch

1. Calorie intake and food quality

Of course, fat storage occurs when you create a calorie surplus (consuming more calories than you burn). Any eating plan that helps create a calorie deficit (consuming fewer calories than you burn) can lead to weight loss. However, researchers have observed a connection between the quality of food choices (more fruits, vegetables, and whole grains) and lower percent body fat.

2. Physical activity

Exercise and daily physical activity help burn calories to avoid a calorie surplus. Strength training exercises, in particular, can help prevent muscle loss as you lose weight.

3. Age

Among the factors that affect body composition, aging may be the most frustrating. People tend to lose muscle and gain body fat around age 30. Even if your weight doesn't change, this shift leads to a higher body fat percentage. It can also result in tighter-fitting clothes, given that a pound of body fat takes up more space than a pound of muscle. Also, a higher proportion of abdominal ("belly") fat accumulates with age, increasing diabetes and heart disease risk.

Of course, when people gain weight with age, most of this weight gained is fat, not muscle, so again, the percent of body fat rises.

4. Sex

Given the same body mass index (BMI), women have about 10% more body fat than men. This difference is likely to support the energy needs of childbearing. Women also have increased body fat during pregnancy and lactation. During menopause, women tend to accumulate more fat around their abdomen.

Testosterone is responsible for the increased muscle mass men have compared to women.

5. Genetics

Genetics account for about 40-70% of the risk of being overweight. In addition to affecting hunger and fullness signals, your genes can influence how and where you store body fat. But, of course, genetics don't equal destiny. Not everyone with the genetic tendency toward becoming overweight does so.

6. Poor sleep

Inadequate sleep isn't just about feeling wiped out the next day. Poor sleep can increase inflammation and insulin resistance, triggering fat storage. Lack of sleep also poses additional challenges for weight loss: increased appetite and food cravings, making it harder to limit calorie intake.

7. Stress

Periods of stress prime your body for fat storage, resulting from your body going into "survival mode." Many studies show an association between higher levels of the stress hormone cortisol and increased fat cell size, formation of new fat cells, and abdominal fat deposits. In addition, stress can trigger emotional eating and make it harder to exercise and prepare healthy foods.

Lifestyle can help overcome all of these factors

Given that many of the above factors are beyond our control, changing body composition can feel like a futile task. However, maintaining regular activity (including cardio and strength training) and limiting calorie intake can help you avoid storing excess body fat. Practicing self-care strategies to improve sleep and manage stress will also help you feel your best and may help reduce body fat storage. If you want to get a grip on specific factors that affect body composition discussed above, check out the links below for expert ideas.

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