Conference Coverage

New findings cast more doubt on ‘fat-but-fit’ theory



– Can you be “fat but fit” if you’re obese but don’t suffer from metabolic syndrome? Some advocates have claimed you can, but new findings presented at the annual scientific sessions of the American Diabetes Association provide more evidence that those extra pounds translate to extra cardiac risk.

Dr. Yvonne Commodore-Mensah

Dr. Yvonne Commodore-Mensah

Fat-but-fit is a misnomer, Yvonne Commodore-Mensah, PhD, RN, assistant professor at Johns Hopkins School of Nursing, Baltimore, said in an interview. “The metabolically healthy obese are not so healthy. [We found] they had a higher risk of heart disease than people who were metabolically healthy and nonobese.”

Studies began supporting the fat-but-fit “paradox” in the late 1990s. They showed “that all-cause and CVD [cardiovascular] mortality risk in obese individuals, as defined by body mass index (BMI), body fat percentage, or waist circumference, who are fit (i.e., cardiorespiratory fitness level above the age-specific and sex-specific 20th percentile) is not significantly different from their normal-weight and fit counterparts” (Br J Sports Med. 2018;52[3]:151-3).

However, a 2017 study had found that “metabolically healthy obese individuals had a higher risk of coronary heart disease, cerebrovascular disease, and heart failure [compared with] normal weight, metabolically healthy individuals” (J Am Coll Cardiol. 2017;70[12]:1429-37). And a 2016 meta-analysis of 22 studies had produced similar results but also found that metabolically healthy obese individuals were better off, cardiac-health–wise, than those of normal weight who were metabolically unhealthy (Eur J Prev Cardiol. 2016;23[9]:956-66).

Dr. Commodore-Mensah and colleagues sought to establish through their study whether there was evidence of subclinical heart disease in people who are considered obese but metabolically healthy (Abstract 272-OR).

They tracked 11,884 participants in the Atherosclerosis Risk in Communities Study (ARIC) from 1990-1992 to 2016-2018. The study, which continues today, includes participants in suburban Minneapolis; Jackson, Miss.; Forsyth County, N.C.; and Washington County, Md.

None of the participants had previous cardiovascular disease at baseline (1990-1992). The researchers divided the participants into four groups at baseline: Nonobese (with metabolic syndrome, 20% of the total number of participants; or without metabolic syndrome, 51%) and obese (with metabolic syndrome, 20%; or without metabolic syndrome, 9%).

The average age range in the groups was 56-57 years. The percentage of women in the groups ranged from 53% to 58%, except for the obese and metabolically healthy group (73%). The percentage of black participants in the groups ranged from 17% (nonobese, metabolically unhealthy) to 45% (obese, metabolically healthy).

“People who were younger, women, and black were more likely to be classified as metabolically healthy obese,” Dr. Commodore-Mensah said.

According to one adjusted model with a median follow-up of 16 years and a total of 3,560 events, obese participants had a higher risk of incident cardiovascular disease, compared with their nonobese counterparts, regardless of whether they had metabolic syndrome.

When compared with the nonobese, metabolically healthy group, the risk grew in the nonobese, metabolically unhealthy group (hazard ratio, .24; 95% confidence interval, 1.12-1.36), as well as in the obese, metabolically healthy (HR, 1.33; 95% CI, 1.15-1.53) and the obese, metabolically unhealthy (HR, 2.11; 95% CI, 1.90-2.35) groups.

The researchers also focused on the cardiac biomarker known as high-sensitive cardiac troponin T (hs-cTnT), which indicates chronic myocardial damage. “This biomarker provides us with a window to the heart,” Dr. Commodore-Mensah said.

According to previous findings reported in 2014, ARIC participants who had hs-cTnT levels of 14 ng/L or higher were much more likely than were those with undetectable levels to suffer from heart failure, death from any cause, and coronary heart disease (JACC Heart Fail. 2014;2[6]:600-7).

Based on an analysis of the hs-cTnT levels in the present study, the researchers believe obese, metabolically healthy participants fell in the intermediate range of excess subclinical myocardial damage, between the nonobese and the obese participants who are also metabolically unhealthy.

“This group is not protected from heart disease,” Dr. Commodore-Mensah said. “They should be targeted, and they would benefit from behavioral changes, such as modifying their diet and increasing physical activity levels.”

The study is funded by the National Institutes of Health. Dr. Commodore-Mensah and six coauthors reported no relevant disclosures. Two coauthors reported various disclosures.

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