Fat is the enemy of dieting, but… losing too much risks ‘this disease’

When dieting, people often pay the most attention to body fat percentage. Body fat percentage refers to the proportion of body fat in the body, and the normal body fat percentages for men and women are 15–20% and 20–25%, respectively. While having too high a body fat percentage is problematic, having an excessively low percentage is also not good for your health.

Excessively low body fat can cause the face to age rapidly. In particular, if subcutaneous fat decreases while skin elasticity has already declined with age, wrinkles are more likely to deepen. Wrinkles make one look older than their actual age. Furthermore, rapidly reducing body fat over a short period can accelerate facial aging because skin elasticity cannot keep up with the rate at which fat is lost. To maintain skin elasticity while losing weight, it is necessary to lose weight slowly and gradually, and to consume a balanced diet of essential nutrients, such as protein and vitamins, to prevent the skin from becoming dry and dull. Getting enough sleep and avoiding stress are also important.

When the body lacks fat, estrogen levels decrease, increasing the risk of osteoporosis. This is because estrogen, primarily produced in the ovaries, is also generated in fat cells and the adrenal glands. Osteoporosis is a disease that occurs when osteoclasts, which destroy bone, outnumber osteoblasts, which build bone. If estrogen fails to function normally, osteoclasts become overactive, and bone resorption is not inhibited, leading to a decrease in bone density. Consequently, the risk of osteoporosis increases.

In addition, a decrease in estrogen increases the risk of infertility and can cause menstrual irregularities. In fact, infertility caused by abnormal weight is known to account for approximately 12% of all infertility cases. Half of these are caused by being underweight.

To manage body fat healthily, it is important to consistently control your diet and exercise. Rather than losing weight rapidly through calorie restriction such as intermittent fasting or low-calorie diets, it is better to adopt lifestyle habits that allow you to maintain your weight in the long term. For example, combining aerobic exercise with strength training helps burn more calories as it increases muscle mass.