Scientists find different types of obesity, confirming that a high BMI does not always indicate health risks

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  • According to a new study published in Metabolism of natureobesity is not just a matter of weight relative to height or body mass index (BMI): there are actually at least four metabolic body types.

  • The research also found that those who fit into the BMI category of overweight or obese are not destined to develop diseases previously thought to be directly related to weight.

For decades, one calculation, the body mass index (BMI), has been used to determine whether someone is overweight or obese. BMI compares weight in relation to height, and when this number is high, doctors are likely to tell patients that they are at risk of health problems and therefore need to lose weight.

It turns out, however, that this equation is not a reliable marker of health outcomes. Some people who fit into the “obese” category, based on BMI, may never receive a disease diagnosis, while others in the “normal” BMI range could have a genetic predisposition to heart disease and other diseases, regardless of their weight.

“It has long been clear to us that there are at least three types of people when it comes to obesity: those who are healthy and obese, those who are obese and have comorbidities, such as diabetes or heart disease, and those who are obese and are on the way to developing comorbidities,” explains Andrew Pospisilik, Ph.D., chair of the Department of Epigenetics and founding member of the Metabolic and Nutritional Programming Group at the Van Andel Institute in Grand Rapids, Michigan. Ride a bicycle. “We wanted to see if we could start to identify the genetic variations in these different ‘types’ of obesity.”

To examine the types of obesity, Pospisilik and his team studied the twins and the ways in which their weight varied over the years. They then tried to mimic their findings in mice.

“Using a purely data-driven approach, we saw for the first time that there are at least two distinct metabolic subtypes of obesity, each with its own physiological and molecular characteristics that influence health,” said Pospisilik. “Our findings in the lab almost replicated the data from the human twins. We again saw two distinct subtypes of obesity.”

Until now, scientists placed people into one of three metabolic types: endomorph (stores fat easily), mesomorph (gains muscle easily), and ectomorph (thin, struggles to gain fat or muscle). The recent findings, however, were published this month in Metabolism of naturedivides people into four metabolic subtypes (two lean-prone and two obesity-prone) that may one day help doctors provide more accurate patient care and inform more accurate ways to diagnose and treat obesity and associated metabolic disorders, Pospisilik explained.

The team also found that of the two obesity-prone metabolic subtypes, one was associated with increased inflammation, which can increase the risk of certain cancers and other diseases, while the other was not. Some genes also appeared to respond to certain triggers, such as lifestyle choices or specific foods, leading to weight gain and disease susceptibility, while others did not.

The science that studies how genes are affected by behavior and the environment is called epigenetics. Pospisilik, an epigeneticist, doesn’t study, for example, which foods or lifestyle choices can alter a person’s weight, but looks for genetic predispositions that coordinate with weight and how that can influence disease.

Unlike genetic alterations, epigenetic changes are reversible and do not modify the DNA sequence. “I like to tell people that all bees are born with the same DNA, but some become worker bees and some become queens. In the end, all queen bees are genetically like other queen bees. How does this happen? Epigenetics are the processes that can guide the same bee DNA to become a queen or a worker, but nothing in between,” said Pospisilak.

Pospisilak and his team found that this same idea applies to humans and their weight and health. While one person is more prone to building muscle, another may be more prone to gaining weight and their diets may be very similar.

“Between the twin studies and the mouse studies, we can really show how each individual can have several genetically pre-programmed pathways available, with lifelong consequences,” Pospisilak explained.

In the end, new research confirms that there’s more to health and fitness than the number on the scale or on a BMI chart.

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