Dropping Weight Beneficial but Some Effects of Obesity Persist

It’s hard for people to completely escape a history of obesity, even when they later achieve a healthy weight.

American adults who once had obesity but later achieved and maintained a healthy body mass index (BMI) normalized some, but not all, of the excess clinical risk associated with obesity in a review of data collected from about 20,000 people during a series of eight NHANES surveys.

Maia P. Smith, MD, reported the findings at the virtual European Association for the Study of Diabetes (EASD) 2021 Annual Meeting.

“For some conditions, such as hypertension and dyslipidemia, the recovery [following a sharp drop in BMI] appears to be total, while for other conditions, like diabetes, the recovery is probabilistic. Some recover, but some don’t,” explained Smith in an interview.

“Weight loss reverses all, or essentially all, of the damage done by obesity in some people, but does not cause full reversal of the harm and does not fully resolve [type 2] diabetes in many others,” added Smith, an epidemiologist in the Department of Public Health and Preventive Medicine at St. George’s University, Grenada.

“The fact that…analyses comparing formerly obese people to normal weight populations demonstrated improvement in population mean levels of hypertension and dyslipidemia is remarkable,” commented Rebecca T. Emeny, PhD, an epidemiologist at the Dartmouth Institute of Health Policy and Clinical Practice in Lebanon, New Hampshire, who was not involved with Smith’s study.

“The observation that the individuals who were able to maintain normal weight after past obesity were still at greater risk for diabetes compared with the normal weight group speaks to the recent discussion of obesity as a metabolic disorder rather than a problem of calories in and calories out,” said Emeny in an interview.

She cited a recent article that proposed a carbohydrate-insulin model for obesity in place of an energy-balance model. This, however, is still somewhat contentious.

Emeny also cautioned that “the results of this study compare populations. The design and analysis do not allow for interpretation of individual risk resulting from changes in weight.”

Those Who Formerly Had Obesity Can Reverse Hypertension, Dyslipidemia

The study by Smith and associates used data collected in the National Health and Nutrition Examination Survey (NHANES), which is performed every 2 years by the US Centers for Disease Control and Prevention.

They used data from eight consecutive surveys starting in 1999-2000 and continuing through 2013-2014, yielding data from nearly 40,000 adults who were at least 20 years old.

In addition to the 326 people who formerly had obesity at some time previously during their life (BMI ≥ 30 kg/m2) but now had a healthy BMI, and 6235 who were consistently at a healthy BMI, they also included 13,710 people who currently had obesity. They dropped the remaining survey participants who did not fit into one of these three categories.

The participants who formerly had obesity averaged 54 years old, compared with a mean age of 48 years among those with current obesity and 41 years among those who currently had a healthy BMI (who had never had obesity). The results showed no differences by sex, but those who formerly had obesity had a much higher smoking prevalence.

The people who reported a healthy BMI (18.5-24.9 kg/m2) after previously having obesity had current prevalence rates of hypertension and dyslipidemia that were, respectively, 8% and 13% higher than the prevalence rates among adults who consistently maintained a healthy BMI — differences that were not significant.

In contrast, people who had current BMIs that indicated obesity had prevalence rates of hypertension and dyslipidemia that were each a significant threefold higher than those with a healthy BMI.

The 326 respondents who formerly had obesity but now were at a healthy BMI had a threefold higher prevalence of diabetes than did the 6235 who consistently had maintained a healthy BMI. This was substantially less than the over sevenfold higher prevalence of diabetes among those who currently had obesity compared with those who always had a healthy BMI.

All these analyses were adjusted for the potential confounders of age, sex, smoking history, and ethnicity.

Quitting Obesity Better Than Current Obesity

The finding that reaching a healthy BMI after a period of obesity could reverse some but not all risks associated with obesity is reminiscent of the effects of smoking, noted Smith.

“Never is better than ever, but quitting,” or dropping weight to reach a healthy BMI, “is better than current,” she concluded.

But Emeny said this interpretation, “while motivating and catchy, places emphasis on individual responsibility and choice rather than on social circumstances.”

Social effects “must be considered when evaluating population-level disparities in obesity-related cardiometabolic risk,” cautioned Emeny.

“‘Quitting’ obesity is much more complicated than individual choice or ability.”

Smith also conceded that her analyses did not correct for the possible confounding effects that changes in diet or physical activity may have had on the observations.

“Neither diet nor physical activity has a well-known summary measure that we could have included as an adjuster,” she explained.

Smith and Emeny have reported no relevant financial relationships.

EASD 2021. Abstract 84. Presented September 29, 2021.

Mitchel L. Zoler is a reporter for Medscape and MDedge based in the Philadelphia area. @mitchelzoler

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