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Weight-loss diet programs prevent premature mortality in adults with obesity

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November 15, 2017

Alison Avenell
Alison Avenell

Adults with obesity who participated in weight-loss diet interventions had a lower risk for premature death compared with control groups, but evidence related to differences in cardiovascular and cancer mortality risks was less strong, according to meta-analysis findings.

“Weight-reducing diets, usually low in fat and saturated fat, may reduce premature all-cause mortality in adults who are obese,” Alison Avenell, MD, of the health services research unit at the University of Aberdeen in Scotland, told Endocrine Today. “Most of the reducing diets also gave advice to increase exercise or provided an exercise program to attend. We do not have evidence to establish whether other forms of weight-reducing diets have this effect, and we cannot dissociate the effects of weight loss from the use of low-fat diets in our study.”

Avenell and colleagues conducted a systematic review and meta-analysis of 54 randomized controlled trials with 30,206 participants to assess whether weight-loss interventions that include a weight-reducing diet affect all-cause, CV and cancer mortality, CVD, cancer and body weight in adults with obesity.

All trials consisted of dietary interventions targeting weight loss, with or without exercise advice programs compared with a control intervention.

Thirty-four trials included data on all-cause mortality, and researchers observed high-quality evidence that there was a decrease in premature mortality with weight-loss interventions (685 events; RR = 0.82; 95% CI, 0.71-0.95). Moderate-quality evidence was observed for an effect of weight-loss intervention on CV mortality (8 trials; 134 events; RR = 0.93; 95% CI, 0.67-1.31), and very low-quality evidence was observed for an effect on cancer mortality (8 trials; 34 events; RR = 0.58; 95% CI, 0.3-1.11).

High-quality evidence on participants developing new CV events was reported in 24 trials (1,043 events; RR = 0.93; 95% CI, 0.83-1.04), and very low-quality evidence on participants developing new cancers was reported in 19 trials (103 events; RR = 0.92; 95% CI, 0.63-1.36).

“Existing weight-loss trials and those in the future need to publish data on long-term clinical outcomes,” Avenell said. “Other types of weight-loss diets (eg, low-carbohydrate, very low-calorie diets) need more evidence from large, well-conducted long-term clinical trials with adequate statistical power to support them. Research is particularly needed on the long-term behavior change techniques that can be used to help people sustain weight loss. However, most research is needed into policies that can change the obesogenic environment to prevent obesity in the first place, and to also support those who have lost weight.” – by Amber Cox

For more information:

Alison Avenell, MD, can be reached at a.avenell@abdn.ac.uk.

Disclosures: The authors report no relevant financial disclosures.

itj+ Perspective

Caroline Apovian
Perspective

This systematic review and meta-analysis of randomized controlled trials of dietary interventions plus or minus exercise looking for weight loss found that weight-reducing diets for obesity in adults is associated with an 18% reduction in premature mortality over the median trial duration of 2 years.

The mean weight loss seen after 1 year was -3.42 kg, 2 years - 2.75 kg and 3 years -2.56 kg, which are roughly equivalent to a 5% weight reduction. The authors were unable to show effects on cardiovascular and cancer mortality.

What is interesting to me is the stark contrast between extreme obesity and the most effective intervention, which is bariatric surgery, and the interventions for other diseases, such as cardiovascular disease manifested by chest pain. For chest pain, one can opt for medication or a surgical intervention, such as stent placement with medication, and the difference in mortality between medications and surgery in this disease was found to be nonsignificant by the COURAGE trial published in the New England Journal of Medicine in 2007 (Boden WE, et al. N Engl J Med. 2007;doi:10.1056/NEJMoa070829).

By contrast, Roux-en-Y gastric bypass surgery has been shown to be effective in producing a 32% weight loss with a maintenance of 25% weight loss after 20 years on average plus a reduction in all-cause and cardiovascular as well as cancer mortality. Yet only 1% of the population in the United States eligible to receive bariatric surgery gets this procedure, while the numbers receiving stent placement for chest pain relative to those eligible are magnitudes higher.

There is a lack of understanding among patients and providers that obesity is a disease and that patients deserve treatment and that this treatment should be covered by insurance whether it be a weight-reducing diet, with or without medications, or for those eligible by BMI, bariatric surgery.

Yes, the BMI is not the best measure of body adipose tissue and inflammation, but it is the most cost-effective means of identifying patients at risk of morbidity and mortality from obesity and its sequelae.

Caroline M. Apovian, MD

Professor of Medicine, Boston University School of Medicine,
Director, Nutrition and Weight Management Center, Boston Medical Center

Disclosure: Apovian reports she is a paid consultant of EnteroMedics.