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Weight Gain After Bypass Not Affected by Diet

Ƶ MedicalToday

SAN ANTONIO -- Lifestyle factors -- including dietary intake, physical activity levels, and treadmill time -- were not predictive of weight regain from 2 to 6 years after Roux-en-Y gastric bypass, researchers found.

Instead, a nonmodifiable factor -- resting energy expenditure -- was the strongest predictor, with a higher expenditure associated with less regain (P=0.0012), according to Lance Davidson, PhD, of the University of Utah in Salt Lake City.

Action Points

  • This study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.
  • Note that in this prospective study none of the evaluated lifestyle measures (diet, physical activity or fitness) at 2 years after surgery predicted 6-year weight change. However, fat free mass and resting energy expenditure were related to weight regain after adjustment for initial weight loss, age, and sex.

He called the results surprising during his presentation at the Obesity Society meeting here.

"Attempts to prevent regain through lifestyle means -- diet or exercise -- may be difficult, possibly due to a reduced metabolic rate in some patients," he said. "More intensive intervention may be necessary for long-term weight maintenance."

Davidson and his colleagues explored the factors associated with weight regain after gastric bypass surgery using data from the prospective Utah Obesity Study. The current analysis included 140 patients who completed all of the assessments at baseline and at 2 and 6 years after the operation. Similar to the larger study population, the subset was 80% female and 88% white, with a mean age of 46.3.

Weight was measured at each time point, and at 2 years, body composition was measured using bioelectrical impedance, resting energy expenditure was measured by indirect calorimetry, and treadmill testing was performed. The patients also completed questionnaires on diet and physical activity levels.

From baseline to 2 years, weight declined from 134.4 kilograms (296 pounds) to 85.6 kilograms (189 pounds). The decline in fat mass was greater than the decline in fat free mass.

As expected with that amount of weight loss, the resting energy expenditure dropped from 2,201 kilocalories per day to 1,736 kcal/day.

Dietary intake also fell from 2,085 to 1,638 kcal/day.

Self-reported physical activity increased after the surgery, although the percentage who met criteria for being physically active went from only 23% to 34%.

The patients were able to spend more time on the treadmill by 2 years (863 versus 581 seconds).

The amount of weight lost during the first two years after surgery represented 36% of the patients' initial body weight. That was largely sustained through 6 years, at which point the average percentage of initial weight lost was 29%.

The researchers examined three lifestyle factors -- dietary intake, physical activity levels, and treadmill time -- and two nonmodifiable factors -- fat free mass and resting energy expenditure -- as possible predictors of weight regain from 2 to 6 years after the surgery.

The three lifestyle factors were not significantly associated with weight regain, whereas both fat free mass and resting energy expenditure were related after adjustment for initial weight loss, age, and sex.

"Maybe we need to work a little harder in order to overcome the effects of resting energy expenditure change and maybe our interventions need to a be a little bit stronger," Davidson said.

He acknowledged some limitations of the study, including the use of self-reported diet and physical activity information, which is subject to inaccurate reporting, particularly in severely obese individuals.

Disclosures

Davison reported that he had no conflicts of interest.

Primary Source

The Obesity Society

Source Reference: Davidson L, et al "Resting metabolic rate and fat free mass, not diet or exercise, predict weight regain 6 years after gastric bypass surgery" OBESITY 2012; Abstract 92-OR.