Introduction
Obesity has long been linked to shorter lifespans, lower quality of life, and increased risk of disabilities due to cardiovascular diseases like diabetes and atherosclerosis. This raised the question: how can some individuals with obesity appear healthy over the long term, whereas others show immediate signs of health problems? The concept of metabolically healthy obesity has caused quite a stir in the medical community and beyond in recent years, as it challenges deeply held beliefs and long-standing understandings. But the recognition of this phenomenon is far from a new discovery! It dates to Jean Vague’s observations in the 1950s that certain individuals with obesity had different predispositions towards diabetes and atherosclerosis, which seemed to be related to where their fat was concentrated on their bodies.
What is the definition of metabolically healthy obesity?
While individuals who have metabolically healthy obesity (MHO) have been extensively researched, a consensus on a definition in adults has only recently been reached. Metabolically healthy obesity (MHO) is defined as a BMI of 30 kg/m2 or higher and no concurrent metabolic disorder or cardiovascular diseases, such as type 2 diabetes or atherosclerotic disease. A more recent definition has been proposed, requiring additional criteria such as serum triglycerides ≤150 mg/dl and HDL-cholesterol serum concentrations higher than 40 mg/dl in men or 50 mg/dl in women.
Do people with “healthy obesity” people exist?
Recent studies show that MHO is found in 35% of the world’s population. However, there were notable differences between regions and various parts of the world. Irrespective of the definitions used and the remarkable regional and gender variation, MHO is not a rare condition.
Long-term studies have suggested that MHO might be a transient state. About 30% of people with MHO develop or convert to a metabolically unhealthy obesity (MUHO) state with cardio-metabolic complications over a 5-10-year period. Aging and additional weight gain are risk factors for this conversion. Fortunately, increasing physical activity and losing weight can increase the likelihood of preserving MHO status.
What are the health risks of “healthy obesity”?
Metabolically healthy obesity is an interesting and complex phenomenon – on the one hand, these individuals are typically free of metabolic signs associated with “unhealthy weight”, yet they still have higher cardiovascular risks than those who maintain a normal weight. However, their cardiovascular risks are lower than those of people with metabolically unhealthy obesity (MUHO). A 2019 study, for example, found that those with metabolically unhealthy obesity (MUHO) are 5-20 times more likely to develop diabetes than those with a ‘metabolically healthy normal weight’. Even for those with metabolically healthy obesity (MHO), there is still a 4-fold increased risk of developing diabetes compared to metabolically healthy normal weight. Similarly, the risk of cardiovascular diseases is 50% greater in people with MHO at baseline than in people who are metabolically healthy at a normal weight. This means that while there are still risks involved with being classified as metabolically healthy obese, they are nowhere near as severe as those associated with those who are metabolically unhealthy.
How to prevent the transition to metabolically unhealthy obesity?
As MHO is not a static condition, attention has now shifted to what factors may predict metabolic deterioration from MHO to MUHO. A study in Spain identified three main factors: an increase in BMI, waist circumference, and waist-to-hip ratio. On the flip side, lifestyle choices like following a healthy diet, regular exercise, and avoiding or quitting smoking prevented the transition to MUO. It’s clear from this that good habits can help maintain our health and protect us from potentially serious conditions like MUO.
Conclusion
There is such a thing as metabolically healthy obesity, but it may be transient and comes with its own risks. The best way to avoid these risks is to maintain a healthy weight through diet and exercise. So, let’s take care of our health and be more mindful of what we eat and how much we exercise.
References
- Blüher, M. (2020). Metabolically Healthy Obesity. Endocrine Reviews, 41(3), 405.
- Smith GI, Mittendorfer B, and Klein S. 2019. Metabolically healthy obesity: facts and fantasies. The Journal of clinical investigation 129:3978-3989.
