A new study looking at ways of maintaining weight loss in subjects who’ve successfully shed pounds through a restricted-calorie diet has found that a higher-protein, lower glycemic index (GI) diet was significantly better than other diets either lower in protein, or with a higher glycemic index, or both.
“We have now shown in a very large European cohort that modifying protein levels and going slightly higher than is usually recommended in terms of protein consumption, and lowering GI, can help people maintain weight loss,” first author on this analysis from the Diet, Obesity, and Genes (Diogenes) study Dr Thomas Meinert Larsen (University of Copenhagen, Denmark) told heartwire .
Whether that ability to maintain a healthy weight–or the means used to attain it–have implications for the heart remains to be seen, he added.
“So far we have looked at body-weight maintenance: whether that translates into a lowered cardiovascular risk, this is of course too preliminary to say.”
Five Diets Compared
Larsen et al enrolled 773 subjects who had lost a mean of 11 kg with a calorie-restricted diet (about 8% of their initial weight) at study onset; for this “weight-maintenance phase” study, they were randomized in a two-by-two factorial design to a control diet, a low-protein/low-GI diet, a low-protein/high-GI diet, a high-protein/low-GI diet, or a high-protein/low-GI diet.
Over a 26-week period, only subjects randomized to the low-protein/high-GI diet regained significant weight (mean 1.67 kg among study completers), whereas those in the high-protein/low GI group actually lost a small amount of weight (mean -0.38 kg). Findings were similar in an intention-to-treat analysis. Those in the high-protein/low-GI group were also the least likely to drop out of the study, whereas dropouts were highest in the group randomized to the low-protein/high-GI diet.
“We could speculate that those who have the best success in terms of weight maintenance were less likely to drop out, but we don’t have the information to say that,” Larsen noted.
In an interesting side finding, the study actually involved whole families, not just overweight adults, such that the entire family was eating the same kinds of recommended foodstuffs, with no restrictions on amount of food. Investigators observed that in families where the participating adult was randomized to the high-protein/low GI diet, the percentage of overweight/obese children in those families actually fell over the course of the study.
Investigators said they have not yet looked at what types of protein people were eating–something likely to be of interest to cardiologists–although Larsen speculated that the most common types of animal protein likely differed across the eight European centers participating in the study. He also predicted that the benefits in terms of weight maintenance would be similar regardless of whether the protein source was animal or vegetable.
“There is an ongoing discussion as to what the real net effect is of saturated fats, as compared with carbs or other fats,” Larsen said, not only for cardiovascular disease, but also for cancer. “We will have to look at our own data for long-term effects, and for cardiovascular risk factors, to give a more solid evaluation of potential good or bad effects concerning cholesterol (from higher protein consumption).”
In an accompanying editorial, Drs David S Ludwig and Cara B Ebbeling (Children’s Hospital and Harvard Medical School, Boston, MA) point out that a number of recent studies have shown no differences in amount of weight loss among different popular diets. That said, “A person’s ability to maintain adherence over time may be influenced by the way in which a diet affects hunger and metabolism,” they write. “Additional research is needed to clarify the mechanisms by which dietary composition regulates body weight and to devise novel strategies to effect behavioral changes.”
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