“Body composition” refers to the relative percentages of fat, muscle, and bone in your body. The term is mostly used by doctors and scientists.
Increasing or maintaining muscle mass and bone density can help you stay fit and active as you get older.
If your body composition isn’t within a healthy range, reducing your body fat percentage could lower your risk of developing health conditions such as heart disease and type 2 diabetes.
Improving your diet, exercising more, and getting better sleep can all make a difference.
How does it affect your health?
Your body composition can influence your risk of developing a range of health conditions.
Having too much body fat is linked to metabolic diseases, like heart disease and type 2 diabetes, as well as some types of cancer.
As you age, your bones may become less dense and you may lose muscle, though your overall weight may not change.
Low bone density can significantly increase your risk of fractures.
Muscle loss can eventually affect how well you can perform day-to-day tasks. If this happens, it can increase your risk of falls, illness, and obesity.
Your body composition also influences your basal metabolic rate (BMR). This is the amount of energy your body uses every day for functions like breathing, sleeping, and blood circulation.
Having more lean muscle tends to increase your BMR, meaning you burn more energy and may store less body fat.
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How can you change your body composition?
Exercise, diet, and sleep all influence your levels of body fat and muscle mass.
If your ratio of fat to muscle mass is too high, doing regular resistance training can help.
Resistance training is also called strength training. It can involve lifting weights, using resistance bands, or doing bodyweight exercises, like squats and push-ups.
To gain muscle through exercise — or to slow down muscle loss as you age — you may need more protein.
Healthy sources of protein include:
legumes, like peas or beans
fish, such as salmon or sea bass
lean, unprocessed meats
dairy, like milk, yogurt, or cottage cheese
nuts and seeds
Try to get your protein in throughout the day. Your body can only use a certain amount to maintain and build new muscle mass, and extra protein may end up as fat.
If you’re looking to reduce body fat, eating patterns like the Mediterranean diet are a healthy approach. They don’t involve restrictive calorie counting.
The Mediterranean diet typically includes:
a wide range of fruits and vegetables
plenty of legumes
extra virgin olive oil
moderate or no alcohol
limited red meat and processed meat
limited foods and drinks with added sugar
At ZOE, we run the largest nutrition science study in the world. We know that our bodies have unique responses to different foods, so a one-size-fits-all approach to nutrition doesn’t work.
Our at-home test assesses the health of your gut and measures how your blood sugar and blood fat levels respond to food. With this information, our personalized nutrition program can help you eat the best foods for you and your health goals.
Learn more about how it works and take our free quiz.
Many experts think sleep processes influence our body composition in important ways.
Here are ways to help you sleep better:
Go to bed and get up at the same times each day.
Try not to sleep during the day.
Get regular exercise.
Get some natural light each day.
Avoid caffeine after lunch.
Don’t spend too long in bed when you’re not sleeping.
Don’t use your smartphone or watch TV in bed.
Make your bedroom quiet, dark, and cool.
What is body fat?
Body fat, or adipose tissue, is more complex than you might think. Beyond fat cells, it’s made up of connective tissue, immune cells, and nerve cells.
There are two types of body fat: subcutaneous fat and visceral fat. Subcutaneous fat is a layer beneath your skin. Visceral fat surrounds your internal organs.
Their layers change as we age. And there are differences when it comes to sex: During and after puberty, visceral fat tends to build up around the waist and belly in males.
In females, subcutaneous fat tends to build up around the hips and thighs. And after menopause, visceral fat levels increase.
Body fat is a form of stored energy — our bodies use it when it’s needed. It also helps:
keep you warm
release hormones to regulate your appetite and metabolism
produce proteins and enzymes involved in your immune system
Having too much body fat, or not having enough, can contribute to a variety of diseases. The visceral fat around your organs is the type that’s mainly associated with these health issues.
Too much body fat
Overweight or obesity increases your risk of developing certain health conditions, including:
high blood pressure
unhealthy cholesterol and blood fat levels
type 2 diabetes
poor mental health
several types of cancer
Too little body fat
Not having enough body fat also increases your risk of some health conditions, including:
low blood pressure
problems with blood flow around the body
low levels of oxygen in the blood
poor wound healing
poor mental health
You can learn more about how your body creates fat by listening to the ZOE Science & Nutrition podcast on fats and oils.
What is muscle?
Muscle is soft tissue that controls our movements, supports our posture, and helps move things around in our bodies.
Most of your muscles are skeletal muscles. These make up around 40% of your body weight.
Skeletal muscles are bundles of individual muscle fibers. They include everything from the large muscles in your legs and arms to the smaller muscles in your face.
And skeletal muscles are also important for your metabolism.
Reduced muscle mass or quality can make you less efficient at managing your blood sugar, increasing your risk of type 2 diabetes.
As we mentioned earlier, you can lose muscle mass and strength as you age. This process is called sarcopenia.
Maintaining a healthy muscle mass as you age can reduce your risk of the associated health issues and protect your quality of life.
Body composition vs. weight vs. BMI
“Body composition” refers to the different percentages of muscle, fat, and bone in your body.
Body weight is just a single number, the total mass of all the different types of tissue in your body. It doesn’t take into account any ratios.
So, people with the same weight could have very different levels of muscle and fat.
This is why some lean, muscular athletes have a high BMI — in the overweight range — even though they’re fit and healthy.
How to measure body composition
If a doctor needs to check your body composition, they might use:
Calipers: This tool pinches folds of skin and fat at different points on your body to measure their thickness. Doctors use calipers to calculate your body fat percentage.
Bioimpedance: This method involves attaching electrodes to you and estimating your body composition based on the rate at which an electrical current travels through your body.
Dual-energy X-ray absorptiometry: This approach is also called DEXA. It involves using low-level X-rays to analyze the amounts of fat, muscle, and bone in different areas.
Magnetic resonance imaging: This is an MRI scan. It involves using a combination of magnetic fields and radio waves to scan your body and identify different types of tissue.
Can you calculate your body composition at home?
You can get an idea of your body composition at home. But these methods aren’t as reliable as clinical approaches:
Online calculators: These use your age, weight, height, and other body measurements to estimate your body fat percentage.
Bathroom smart scales: These use electrical currents to measure the amount of water in your body. It’s the same principle as a clinical bioimpedance machine but less accurate.
Waist circumference: Measuring your waist and comparing it to guidelines can help you tell if you’re at risk of obesity-related health conditions.
Waist-to-hip ratio: Dividing your waist measurement by your hip measurement gives you a single number. This can help predict your risk of certain illnesses.
There’s no single expert agreement about a healthy body composition. But some health organizations do have guidelines about body fat percentage.
The American Council on Exercise, a nonprofit group, lists these ranges for fat:
Safe minimum: 10–13%
Safe minimum 2–5%
A healthcare charity in the United Kingdom, Nuffield Health, notes that a “normal” body fat percentage depends on your age, but it’s in the range of 33–36% for females and 19–25% for males.
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Body composition is the percentage of fat, muscle, and bone in your body.
These ratios can have a huge impact on your health, influencing your risk of developing chronic and age-related diseases.
The good news is that routine changes, like exercising more, eating well, and getting better sleep, can improve your body composition and your health.
To get an accurate idea of your body composition, speak with your doctor about clinical approaches.
In the meantime, measuring your waist circumference or calculating your hip-to-waist ratio can give you a broad idea of whether you might need to make some changes to your routine.
About adult BMI. (2022). https://www.cdc.gov/healthyweight/assessing/bmi/adult_bmi/index.html
Accuracy of smart scales on weight and body composition: Observational study. JMIR mHealth and uHealth. (2021). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8122302/
Adherence to the Mediterranean diet and body fat distribution in reproductive aged women. European Journal of Clinical Nutrition. (2013). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3594052/
Assessing your weight. (2022). https://www.cdc.gov/healthyweight/assessing/index.html
Association between actigraphic sleep metrics and body composition. Annals of Epidemiology. (2015). https://www.sciencedirect.com/science/article/abs/pii/S1047279715001854
Body fat percentage, body mass index and waist-to-hip ratio as predictors of mortality and cardiovascular disease. Heart. (2014). https://heart.bmj.com/content/100/20/1613.short
Body fat percentage: The hidden health number. (2019). https://www.nuffieldhealth.com/article/body-fat-percentage-the-hidden-health-number
Caution, “normal” BMI: Health risks associated with potentially masked individual underweight. EPMA Journal. (2021). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8368050/
Health effects of overweight & obesity. (2022). https://www.cdc.gov/healthyweight/effects/index.html
Influence of a Mediterranean dietary pattern on body fat distribution: Results of the PREDIMED-Canarias intervention randomized trial. Journal of the American College of Nutrition. (2016). https://pubmed.ncbi.nlm.nih.gov/27314172/
Magnetic resonance imaging (MRI). (n.d.). https://www.nibib.nih.gov/science-education/science-topics/magnetic-resonance-imaging-mri
Measuring obesity. (n.d.). https://www.hsph.harvard.edu/obesity-prevention-source/obesity-definition/how-to-measure-body-fatness/
Obesity and cancer. (2022). https://www.cancer.gov/about-cancer/causes-prevention/risk/obesity/obesity-fact-sheet
Osteoporosis. (2022). https://www.niams.nih.gov/health-topics/osteoporosis
Percent body fat calculator: Skinfold method. (n.d.). https://www.acefitness.org/resources/everyone/tools-calculators/percent-body-fat-calculator/
Physiology, muscle. StatPearls. (2023). https://www.ncbi.nlm.nih.gov/books/NBK532258/
Protein consumption and the elderly: What is the optimal level of intake? Nutrients. (2016). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4924200/
Sarcopenia and its implications for metabolic health. Journal of Obesity. (2019). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6431367/
Sleep duration and obesity among adults: A meta-analysis of prospective studies. Sleep Medicine. (2014). https://www.sciencedirect.com/science/article/abs/pii/S1389945714003906
Sleep duration and waist circumference in adults: A meta-analysis. Sleep. (2015). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4507732/
Subcutaneous adipose tissue & visceral adipose tissue. Indian Journal of Medical Research. (2019). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6702693/
The benefits of strength training and tips for getting started. (2017). https://pubs.nmsu.edu/_i/I111/
The effect of resistance training in healthy adults on body fat percentage, fat mass and visceral fat: A systematic review and meta-analysis. Sports Medicine. (2022). https://link.springer.com/article/10.1007/s40279-021-01562-2
The effects of the Dietary Approaches to Stop Hypertension (DASH) diet on metabolic risk factors in patients with chronic disease. Nutrition, Metabolism and Cardiovascular Diseases. (2021). https://www.sciencedirect.com/science/article/abs/pii/S0939475321002532
The potential role of sleep in promoting a healthy body composition: Underlying mechanisms determining muscle, fat, and bone mass and their association with sleep. Neuroendocrinology. (2022). https://karger.com/nen/article/112/7/673/825396
The primary vascular dysregulation syndrome: Implications for eye diseases. EPMA Journal. (2013). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3693953/
The utility of body composition assessment in nutrition and clinical practice: An overview of current methodology. Nutrients. (2021). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8399582/
Tips for better sleep. (2022). https://www.cdc.gov/sleep/about_sleep/sleep_hygiene.html