Not all people with obesity have the same characteristics or the same risks to your health. At first this might seem obvious, but the truth is that until now the majority of medicine has relied solely on the body mass index (BMI) to diagnose obesity, thus ignoring a series of important characteristics.

Two types of obesity

A study prepared by an international team of scientists and published in the prestigious academic journal Nature Metabolism has elaborated a new classification of obesity which divides it into two categories based on its phenotypic characteristics, identifying the consequences that each of them has on health.

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The difference between them is essentially metabolic. In fact, the work identifies four metabolic subtypes that influence body mass, two of them more prone to thinness and two more prone to obesity, but with different physiological and molecular traits.

The most interesting of this classification, made from data of twin brothers extracted from the project TwinsUK, it arrives with the verification of the same carried out in mouse models. And it is that being framed in one or another metabolic subtype does not seem to be a consequence of the diet, environment or genetics.

The most severe is activated by epigenetic chance.

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There is a widespread idea, not only among laymen but also among scientists themselves, that the characteristics of an organism (or at least the vast majority of them) are fundamentally determined good for its genetic code or by various environmental factors.

In recent years, however, more and more evidence has emerged that this is not entirely the case. In fact, and as the authors of the article point out, some studies carried out on identical twins seem to indicate that up to 50% of the variation in complex traits not attributable to these sources, which is known as unexplained phenotypic variation (UPV). And this would be the case of the metabolic subtypes to which the researchers refer.

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One of the most popular explanations is that these variations would be mediated by the epigenetics, which is the set of very complex processes that determine the way in which genes are expressed (so to speak, the way in which the information they contain materializes). Following this explanation, some subtypes would be activated, at least apparently, by chance.

Higher levels of inflammation and increased risk of cancer

In any case, these two types of obesity have a fundamental difference. One of them is characterized by an excess of fatty tissue, while the other by increases in both fat and lean mass. And, contrary to what one might imagine, it is the second that is associated with a greater risk of suffering from other diseases, and it is one of the subtypes that would be epigenetically activated by chance.

This happens because the second of the subtypes is associated with greater inflammation, which, when chronic, has a long series of well-documented negative effects on the body. For example, this pattern of obesity is related to an increased risk of cancer.

Be that as it may, the authors of the work hope that these discoveries will be applied to the prescription of more appropriate and effective treatments, taking into account the own characteristics of each patient.


Yang CH, Fagnocchi L, Apostle S et al. Independent phenotypic plasticity axes define distinct obesity sub-types. Nat Metab (2022).