Our body’s fat content tends to increase with age, although this is not inevitable. Old natives of South Sea Islands are as slim as their young, and as active and child- like. Their use of unrefined foods, active life-style, simplicity, and sunny disposition help them remain slim into old age.
On the average, fat accounts for about 15% of the total weight of males, and about 22% of the weight of females. The tendency for women to carry more fat than men evolved during ice ages or even more primitive times, when a primary female role was to produce offspring under living conditions characterized by fluctuating food supplies. It was important for them to store in their body the energy (fat) necessary to complete fetal growth even if the food ran out. Now that food supplies are more stable, the climate warmer, and procreation no longer their main purpose, women still carry the genes and hormones adapted for survival in ice ages, perhaps in preparation for future chills.
Female hormones, responsible for the extra fat that women carry, also protect women from the deleterious cardiovascular effects of fats. Women suffer heart attacks and strokes only one-third as often as men, until their hormones fade at menopause. Within 6 to 10 years after menopause, women become as prone as men to cardiovascular disease. The edge of obesity is considered to be 23% of body weight as fat for men, and 32% of body weight as fat for women.
Some people have excessive fat deposition because of inherited genetic traits. Such mutations are rare, occurring in less than 5 per 1000 in the population. Most of us cannot hide behind our genes on this one. About 400 per 1000 of adult North Americans and Europeans are overweight, largely due to calorie-rich, nutrient-poor diets and inadequate exercise.
Compared to fluctuating fat levels, proteins constitute a fairly constant 12% of the weights of both genders, less than fat on the average. Excess proteins are converted into stored fat. Carbohydrates – glucose in our blood, and glycogen stored in tissues, muscles, and liver – make up only 0.5% of body weight. Carbohydrates above this low level are turned into fat. Minerals make up about 3.5% of body weight.
On average then, fat is the most abundant body component next to water. Nature chose wisely to store energy reserves in this efficient way. Each gram of fat stores more than twice as much energy as the same weight of protein or carbohydrates. Furthermore, while most cells contain about 70% water, our fat cells contain up to 70% fat and very little water. Thus fat and fat cells store energy for future use in an extremely economic and efficient way.
Fat tissues store more cholesterol than other tissues except our brain, whose cholesterol content is even higher than that of fat tissues.