Sumithran et al recently published an article in NEJM wherein they studied 34 adults (originally 50 subjects, but 34 in the end) with an average baseline BMI of 34.7 to assess regulators of appetite (leptin, ghrelin, peptide yy, gastric inhibitory polypeptide, glucagon-like peptide l, amylin, pancreatic polypeptide, cholecystokinin and insulin) and subjective ratings of hunger throughout a 10 week weight-loss program and throughout a year following.
It had previously been shown that some of the peripheral hormonal signals as well as energy expenditure changed significantly in periods of caloric restriction, promoting weight regain, so the purpose of this study was to determine if this would be the case with prolonged maintenance of weight reduction.
This is important because many who attempt to lose weight and have an initial loss due to calorie restriction are unable to maintain their decreased weight and regain the weight lost. There is a “high rate of weight regain after diet-induced weight loss.” Many attribute this to lack of self-control, but if regulators of appetite remain changed, this would attest to a physiological reaction.
For 8 weeks subjects were put on 500-550 calories per day (optifast and some non-starchy veggies), which they call a “very-low-energy” diet.
I’d say it’s more like starvation and completely unnecessary. I think weight loss and potential hormonal changes from such an extreme deficit could confound findings and affect the results. I know there are other longer-term programs, like the HCG diet, that have a similar caloric intake, but most obese people do not go on such extreme diets, so I question the generalizability of findings in these obese individuals to the obese population as a whole.
For weeks 9 and 10, subjects who lost 10+% of their baseline body fat were gradually put on regular foods to stabilize their weight and discontinue further weight loss.
At the end of week 10, subjects no longer consumed the optifast shakes, and a dietician counseled individuals on what their caloric should be based on their energy expenditure and recommended low GI carbs, a reduced intake of fat and 30 minutes of exercise most days of the week.
Besides my issues with the calorie intake, I hate that body composition was measured via a Tanita scale. Scales are so inaccurate, and worse, inconsistent, as body fat measure. I am not sure why DEXA scans or something known to be more accurate was not used. Therefore, in my opinion, these numbers are crude estimates as opposed to hard data. At least the subjects did fast overnight before and consistently did so before each of the three tests (baseline, 10 weeks, 62 weeks), but I still find this method completely insufficient.
Many of the hormones, peptides and nutrients involved in one’s body weight regulation changed and lasted for 12 months after weight less, even after some weight was regain, showing that it’s not all about behaviors or willpower, but there were physiological changes.
A decreased energy expenditure lasted the full year.
At the end of week 10, the average weight loss was 13.5 (14% of their baseline weight) and body fat lost was 9.8%, and 7.9 kg and 5.3%, respectively, at the end of week 62, so subjects had gained some weight and body fat back, but were still 8.2% their initial weights and at a lower body fat. Everything was higher at week 10, which is when subjects first went off the supplement.
I want to note that no behavioral measures were involved, so we don’t know if subjects went back to old habits at all or if all results were based on the physiological changes, which, of course, were real. We don’t know how many calories subjects consumed, if they worked out, etc.
All subjective appetite-related factors – hunger, desire and urge to eat, prospective consumption - had increased at a statistically significant level from baseline to weeks 10 and 62, with preoccupation with thoughts of food increasing at week 10, but increasing substantially and at a statistically significant level at week 62. Interestingly, fullness didn’t change from baseline to the other two test points, but significantly decreased at week 62 than at week 10.
The authors suggest that medications might be necessary to manage long-term weight loss in obese individuals. People who continue to be obese after weight loss suggests that “there is an elevated body-weight set point in obese persons that efforts to reduce weight below this point are vigorously resisted,” a point which I agree with (in general, not just with obese people).
My concerns with the study have been noted above, but I do still think this is a useful study and has potential implications.
randi morse, randi.morse@gmail.com, newton, ma
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