LONDON | Body fat is often treated as something to lose, but medical research shows that having too little of it can also threaten health, affecting hormones, reproductive function, bones, temperature regulation and the body’s ability to maintain adequate energy reserves.
A recent BBC Future report examined the lesser-known risks of extreme leanness, noting that fat tissue is not simply stored energy. It is an active endocrine tissue that produces and influences hormones and plays an important role in regulating metabolism and other bodily functions.
When food intake and energy availability remain too low, the body can begin conserving energy by reducing functions that are not immediately necessary for survival. Research on relative energy deficiency in sport has documented changes involving reproductive hormones, thyroid hormones, insulin, growth-related hormones and metabolism in people whose energy expenditure substantially exceeds their intake.
One of the clearest effects can occur in the reproductive system. Studies have long found that excessive weight loss, restrictive dieting and intense exercise can disrupt the hypothalamic signals that control reproductive hormones. In women, this can lead to irregular or absent menstrual periods and reduced fertility.
The consequences can extend to the skeleton. A 2024 study of women with functional hypothalamic amenorrhea found that 15 percent had low bone mass in the spine or hip, with poorer bone measurements associated with longer periods of weight loss and lower body composition measures. Other research has linked prolonged energy deficiency and hormonal disruption with reduced bone density and increased risk of stress injuries and fractures.
Fat also helps the body respond to changes in energy availability and temperature. The hormone leptin, produced largely by fat tissue, signals the brain about the body’s energy stores. When energy availability becomes too low, reduced leptin and other hormonal changes can contribute to suppression of reproductive and metabolic functions.
The problem is particularly relevant to athletes and people pursuing extremely lean physiques. Sports medicine researchers have described a condition known as Relative Energy Deficiency in Sport, or RED-S, in which inadequate energy intake relative to exercise affects multiple body systems. It can occur in both women and men, although some consequences differ by sex.
Historical research also helped establish that a certain level of body fat and adequate energy availability are important for normal reproductive function. Studies of athletes and women experiencing excessive weight loss found that menstrual disruption could occur when the body’s energy reserves became insufficient, with improvement often following restoration of energy balance.
This does not mean that higher body fat is automatically healthier. Excess body fat carries its own well-established health risks, and body-fat requirements vary with age, sex, genetics, activity level and overall health. The concern raised by the latest research is the pursuit of extreme fat loss without sufficient nutrition or recovery.
For people who are losing weight rapidly, exercising heavily while eating very little, experiencing menstrual changes, persistent fatigue, feeling unusually cold or suffering repeated injuries, health professionals can assess whether inadequate energy availability or another medical condition is involved.
The broader message from the evidence is that body fat is not merely an aesthetic measure. Maintaining sufficient energy stores and nutritional intake is part of keeping the body’s hormonal, skeletal and metabolic systems functioning normally.
Paraluman P. Funtanilla
Paraluman P. Funtanilla is Tutubi News Magazine's Marketing Specialist and is a Contributing Editor. She finished her degree in Communication Arts in De La Salle Lipa. She has worked as a Digital Marketer for start-up businesses and small business spaces for the past two years. She has earned certificates from Coursera on Brand Management: Aligning Business Brand and Behavior and Viral Marketing and How to Craft Contagious Content. She also worked with Asia Express Romania TV Show.
- Paraluman P. Funtanilla
- Paraluman P. Funtanilla
- Paraluman P. Funtanilla
- Paraluman P. Funtanilla
