The modern health narrative focuses almost obsessively on reducing body fat. Metrics such as BMI, body fat percentage, and body weight dominate both the medical field and media coverage. Obesity is rightly recognized as a risk factor for many lifestyle-related diseases, yet this approach often overlooks an equally important—and perhaps even the most important—aspect of metabolic health: the quantity and quality of muscle mass.
An increasing number of studies conducted since 2020 suggest that the mere presence of body fat does not determine disease risk to the extent previously believed. Body composition is key, particularly the ratio of fat mass to fat-free mass, including muscle mass.
Skeletal muscles account for approximately 30–50% of an adult’s body weight and are one of the most important metabolic organs.
They are responsible for:
- storage and utilization of glucose (approximately 70–80% of postprandial glucose uptake),
- regulation of insulin sensitivity,
- the production of myokines—compounds with anti-inflammatory effects,
- maintaining basal metabolic rate,
- maintaining body posture (keeping the body upright),
- thermoregulation,
- motor skills,
- protection of internal organs (they form a protective layer around delicate organs).
Research highlights that muscles are the body’s primary “metabolic buffer.” A lack of muscle mass leads to, among other things, impaired glucose homeostasis, increased inflammation, and a decline in metabolic function.
Sarcopenia, or the loss of muscle mass and function, was once associated primarily with aging. Today, we know that it also affects younger people—especially those who lead sedentary lifestyles. Epidemiological studies from 2021–2024 indicate that:
- the increasing prevalence of so-called "secondary sarcopenia" in people under the age of 50,
- the link between low physical activity and a loss of muscle mass, regardless of age,
- an increase in the number of people classified as "skinny fat" (normal body weight but low muscle mass and high levels of visceral fat)
- an insufficient intake of protein in the diet.
Although BMI is useful in population studies, it does not distinguish between fat tissue and muscle tissue. As a result:
- A person with a normal BMI may have low muscle mass and a high metabolic risk,
- A person who is overweight but has a high muscle mass may be metabolically healthy.
Research in recent years has introduced concepts such as:
• TOFI (Thin Outside, Fat Inside) – slim people with high levels of visceral fat,
• MUHNW (metabolically unhealthy normal weight) – individuals of normal weight but with metabolic disorders.
In both cases, the key factor is a lack of muscle mass, not body weight itself.
Resistance training is currently considered one of the most effective tools for preventive health care.
Research shows that:
- Just 2–3 sessions a week significantly improve insulin sensitivity,
- Strength training reduces inflammation regardless of fat loss,
- Increasing muscle mass improves blood sugar control even without a change in body weight.
The following are also of key importance:
- an adequate protein intake (at least 1.6–1.8 g/kg of body weight),
- physical activity during the day,
- sleep and recovery.
In light of current research, building and maintaining muscle mass should be one of the cornerstones of preventing lifestyle-related diseases.
Increasing muscle mass:
- improves glucose and lipid metabolism,
- reduces the risk of metabolic syndrome,
- has a protective effect on the cardiovascular system,
- supports mental health and cognitive function.
Importantly, these effects occur regardless of changes in body fat, which challenges the traditional approach
focused solely on weight loss.
Although excess body fat remains a significant risk factor, a growing body of scientific evidence suggests that a lack of muscle mass may be a more fundamental health problem of our time. Muscles play a key role in regulating metabolism, and a lack of muscle mass leads to a range of disorders that increase the risk of chronic diseases and shorten life expectancy. Metabolic health is not just a matter of how much we weigh, but above all, what our bodies are made of.
https://www.researchgate.net/profile/Irena-Maniecka-
Bryla/publication/281322323_The_Obesity_Epidemic_in_the_21st_Century/links/55e2405d08ae2fac471f9399/The-Obesity-Epidemic-
obesity-in-the-21st-century.pdf
https://pubmed.ncbi.nlm.nih.gov/34858351/
https://link.springer.com/article/10.1186/s13098-025-01998-w?utm_source
Prepared by: Wiktoria Kubicka
