What is body composition?
The non-fat part of your body is called lean tissue, which includes your muscle, water, bone and organs. Lean tissue is metabolically active tissue, the tissue that burns calories all day. The more lean tissue you have, the higher your resting metabolic rate will be.
The fat part of your body is a storage form of energy and has a very low calorie demand.
In my opinion after helping thousands of patients, a healthy lean percent body fat for women is 21-24%. A healthy lean percent body fat for men is 14-17%. If you seek a leaner physique with more definition, then the ideal percent body fat is lower i.e. 14-20% for women, 8-12% for men.
There is a body fat percentage that is too low and deemed unhealthy i.e. less than 12% for women, and less than 3% for men. This is due to reduced mechanical and thermoregulatory benefits, and cell membrane and hormone dysfunction.
I'm 56 year old, and have 12% body fat. I'm not an athlete, but I consider myself lean and fit, and my blood markers and endothelial function are ideal. I sleep well, am vital, and have more than enough physical and mental energy for my needs.
What is body composition assessment?
Body composition testing determines how much of your body is and isn't fat.
There are many ways to assess body composition, each with their own advantages and disadvantages. These techniques include:
hydrostatic underwater weighing
air displacement plethysmography
dual energy X-ray absorptiometry
isotope dilution hydrometry
magnetic resonacnce imaging
bioelectric impedance analysis
What is bioelectric impedance analysis?
BIA determines the electrical impedance or opposition to the flow of an electric current through body tissues which can then be used to calculate an estimate of total body water (TBW). TBW can be used to estimate fat-free body mass and, by difference with body weight, body fat mass.
Why is increased fat mass bad?
Fat tissue is unhealthy for three mainreasons. Firstly, fat tissue, especially fat fat cells, release hundreds of adipokines, which are molecules that promote inflammation and ill-health throughout the body. They promote cardiovascular disease, cancer, dementia, osteoporosis and mental health disease. Secondly, in our society, increased fat mass can lead to social discrimination, fewer employment opportunities, low self-esteem and depression. Thirdly, it increases the mechanical load on joints, leading to earlier osteoarthritis, especially in the hips, knees and ankles.
Why is increased muscle mass good?
Muscle is not just present to move the skeleton and be aesthetically pleasing. Healthy muscle cells release over 700 myokines that promote the health of the rest of the body. For instance, one myokine, Brain-derived Neurotrophic Factor, causes the growth of new brain cells. Also, muscle cells are very metabolically active, using energy 24 hours a day, during exercise, rest and sleep. In our environment of calorie excess, this decreases the risk of fat accumulation.
Body weight is a poor indicator of the amount of muscle and fat present.
What is subcutaneous fat?
Subcutaneous fat is the fat cells that lie just beneath the skin. They can be assessed by the thickness of the pinched skin fold.
What is visceral fat?
Visceral fat is the fat that lies in the abdomen, in and around the abdominal organs. It is particularly inflammatory, and decreases the function of the abdominal organs and all other body tissues. Inflammation causes wear and tear, and is the commonest cause of death in the West via it's effect on blood vessels (heart attack, stroke), brain cells (dementia), DNA (cancer) and immune dysfunction (autoimmunity i.e. rheumatoid arthritis, multiple sclerosis, Hashimoto's thyroiditis, vitiligo, psoriasis, lupus, ulcerative colitis, Crohn's Disease etc). Visceral fat is harder to assess.
What is skinny fat?
A skinny fat person looks normal, but has a relatively low muscle mass and a high fat mass. They have the poor metabolic health and increased degenerative disease risksof a fat person.
Why is body weight a poor measure of body composition?
Body weight is influenced by the amount of all tissue types present. It doesn't differentiate between the relative amount of the different tissue types. The relative amounts of tissues, particularly lean and fat mass, are a major marker of metabolic health.
Why is body composition a good marker of metabolic health?
Body composition analysis identifies the muscle mass (good) and fat mass (bad), and can be tracked over time to assess the effectiveness of a health program. A low percent body fat with good muscle mass, reflects a healthy metabolism. A good body composition contributes to health by minimising inflammation in the body and physical load on the joints, and is also a sign of a healthy metabolism (gastrointestinal and hormonal health), as well as a good lifestyle (diet, rest, sleep, movement, exercise etc).