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New research cautions that having metabolically healthy obesity still raises the risk of disease. Malandrino/Getty Images
  • Obesity affects people all over the world and puts them at risk of developing certain health problems.
  • Metabolically healthy obesity (MHO) describes when a person has obesity but also a healthy metabolic profile.
  • New research suggests that people with obesity but who are also metabolically healthy are still at higher risk of health problems such as heart failure and respiratory diseases.

Obesity is prevalent in populations all over the world. In 2017–2018, 42.4% of the population of the United States had obesity.

In determining someone’s risk of certain conditions, medical professionals do not only look at a person’s weight. They also examine metabolic profiles, which look at other health risk factors, including cholesterol levels, blood glucose levels, and blood pressure.

A new study in the journal Diabetologia examined health risks for people who have obesity but who lack other metabolic risk factors, such as high blood pressure and high cholesterol.

The findings suggest that people who have obesity should still seek to maintain a moderate weight even if they lack other risk factors for poor health outcomes.

People with obesity are at increased risk of several health problems. Maintaining a moderate weight can help people lower their risk of conditions such as type 2 diabetes, stroke, coronary artery disease, and high blood pressure.

People with obesity have a body mass index (BMI) of 30 or greater. Healthcare professionals calculate BMI by taking a person’s weight in kilograms and dividing it by their height in meters. Although it is not a perfect standard, using BMI as a general tool can help determine if a person is maintaining a moderate weight.

Risk factors for poor health vary. Research is ongoing about risk factors that often coincide with obesity. This has contributed to the creation of the term MHO. There is not always a strict criterion for this term, but someone with MHO typically has obesity but does not have metabolic syndrome.

A person may receive a diagnosis of metabolic syndrome when they have three or more of the following:

  • obesity
  • low levels of high-density liproprotein (HDL) cholesterol
  • high levels of triglycerides
  • high blood pressure
  • high blood glucose levels

The prospective cohort study in the United Kingdom sought to determine whether or not people with MHO are still at greater risk of health problems such as diabetes, heart failure, respiratory diseases, and atherosclerotic cardiovascular disease.

The researchers classified the participants as having MHO if they had normal levels of four or more of the following:

  • blood pressure
  • C-reactive protein
  • triacylglycerols
  • low-density lipoprotein cholesterol
  • HDL cholesterol
  • hemoglobin A1C, which measures the person’s average blood glucose level over a period of around 3 months

In all, 381,363 people participated in the study. After measuring the factors listed above, the researchers divided the participants into four main categories:

  • metabolically healthy non-obesity
  • metabolically unhealthy non-obesity
  • MHO
  • metabolically unhealthy obesity

For some aspects of the analysis, the researchers put those who fit into the non-obesity classifications together in the same group.

They note that some individuals transitioned from having MHO to having metabolically unhealthy obesity, and they explain these changes in the study’s results. In fact, over one-third of the participants who started out as having MHO became metabolically unhealthy in 3–5 years.

In the study, the researchers accounted for various elements of the participants’ demographics, lifestyle habits, and socioeconomic factors.

They examined the prevalence of several health problems and mortality in each group, following up with participants in an average of 11.2 years. The researchers noted the prevalence of the following:

  • diabetes
  • incident/fatal atherosclerotic cardiovascular disease
  • incident/fatal heart attack
  • incident/fatal stroke
  • incident/fatal heart failure
  • incident/fatal chronic obstructive pulmonary disease (COPD)
  • all-cause mortality

The results suggest that the individuals with MHO were at higher risk of diabetes, incident/fatal atherosclerotic cardiovascular disease, heart failure, respiratory diseases, and all-cause mortality than those who fell within the metabolically healthy non-obesity control group.

Overall, the study found that when compared with the metabolically healthy participants without obesity, participants with MHO were:

  • 4.3 times more likely to develop type 2 diabetes
  • 18% more likely to have a heart attack or stroke
  • 76% more likely to have heart failure
  • 28% more likely to have respiratory disease
  • 19% more likely to have COPD

For the most part, those with metabolically unhealthy obesity had the highest risk of all health problems, followed by those with metabolically unhealthy non-obesity, followed by those with MHO. This situation was different for heart failure and respiratory diseases.

Study co-author Dr. Frederick Ho told Medical News Today:

“We found that people with MHO had [an] even higher risk of heart failure and respiratory diseases compared with people who had normal weight but unhealthy metabolic profile. This reinforces the adverse consequences of obesity to be multidimensional and go beyond the usual metabolic health markers.”

Due to the nature of the study, the researchers might have overlooked some areas of data collection, such as the participants’ family history of certain conditions. Therefore, it is possible to use the study results to generalize relative risk but not to determine absolute risk.

Some other limitations include using only hemoglobin A1C in metabolic analysis instead of including other metrics, such as fasting glucose levels or insulin resistance. Also, the study used a strict definition for MHO and did not take other definitions into consideration.

The results indicate that people who have MHO have a higher risk of health problems than those who maintain a moderate weight and a healthy metabolic profile. The researchers encourage people to try to maintain a moderate weight regardless of metabolic profile.

They also find the term MHO misleading. Dr. Ho told MNT:

“Going forward, we should avoid using the term [MHO], as it doesn’t communicate the associated health risk accurately. People who [have obesity], regardless of current metabolic profile, should be encouraged and supported to manage their weight. Meanwhile, even though the MHO label is not useful, future studies can explore how we can make use of metabolic and other health markers to assist clinical management.”