Boost Satiety With High Protein Meals on HWN RESEARCH

A new meta-analysis of diet studies confirmed that a meal high in protein can help people feel more full afterward, which might help them to maintain or lose weight.

Whether the protein came in the form of yogurt, omelets, milk, or soy, participants of most studies reported greater feelings of satiety 2-4 hours after consuming a high-protein meal compared with those who ate a low- or medium-protein meal, said investigator Richard Mattes, PhD, of Purdue University in W. Lafayette, Ind., and colleagues.

Several scholarly reviews of evidence related to protein and weight management and satiety have been published, but none has focused exclusively on the proposed primary mode of action, enhanced fullness. This was the aim of the present meta-analysis," Mattes and colleagues said in the Journal of the Academy of Nutrition and Dietetics.

A good deal of evidence suggests that protein activates satiety hormone release and so should be most strongly tied with fullness ratings," Mattes said in a statement, "but individual studies are often conducted in small populations or with different approaches that can make interpretation of results challenging. Our study combined multiple experiments to confirm the presence of an effect.

However, the meta-analysis covered only five studies due to strict inclusion criteria and had other important limitations, Mattes and colleagues noted.

These analyses indicate that higher protein preloads increase fullness ratings more than lower protein preloads. This conclusion stems from a formal meta-analysis on a limited number (n=5) of published studies and is supported by a directional effect vote-count assessment with a larger (n=28), albeit still small, number of trials relative to the published literature, Mattes and colleagues said.

Nevertheless, This property of protein may hold nutritional implications," the investigators argued. "Greater fullness could contribute to improved quality of life by abating unpleasant appetitive sensations, and protein-mediated augmentation of fullness may also translate to lower energy intake. If this holds across a diet and over time, it may aid in the loss or maintenance of body weight.

The meta-analysis included only interventional studies with healthy human participants using a preload design and whole dietary protein (e.g., yogurt or omelets, not amino acid supplements) as the intervention. Furthermore, included studies had to use fullness as an outcome, reported as an area under the curve (AUC) for 2-4 hours after the test meal.

For the larger directional analysis, studies did not have to report fullness as AUC values 2-4 hours afterward but could measure fullness in a variety of ways at a variety of times after the test meal. In this analysis, the investigators determined only whether the studies found that high-protein meals resulted in more, less, or the same feeling of fullness in study participants compared with low-protein meals.

The five-study meta-analysis indicated higher protein preloads had a greater effect on fullness than lower protein preloads (overall effect estimate: 2,435.74 mm-240 min., (95% CI 1,375.18 to 3,496.31 mm-240 min.; P<0.0001).

In the directional analysis, 11 of the 28 studies reported that protein preloads had a significant positive effect on fullness (P<0.05 for each study). The other 17 studies reported no significant protein effect. However, the researchers added, "A sign test indicated evidence in favor of a positive direction (P<0.01). Therefore, the results from the directional analysis support the meta-analysis results," Mattes and colleagues concluded.

The investigators noted several limitations to their analyses, chief of which was "both analyses were based on a very limited subset of published studies in the literature." Limiting their analyses to studies with similar designs, methods, and outcome measures may have left out important nuances, such as different responses to proteins in different forms or under different conditions, they said.

Another limitation is the analyses did not assess potential different effects of animal versus plant proteins on feelings of fullness, Mattes and colleagues said.

And the researchers noted the possibility of publication bias. Trials yielding null or counterintuitive negative findings may not be submitted for publication and may not be rated as highly by reviewers, so they may not be adequately represented in the literature. The limited number of trials included in this analysis precluded a meaningful assessment of potential publication bias, they said.

Though this study did not specifically evaluate dieters, feeling fuller could help to reduce food intake, an important factor when dieting," Mattes said in a statement. "If these effects are sustained over the long-term -- and our study only looked at short-term effects -- increased protein intake may aid in the loss or maintenance of body weight.

Source: Medpage, HWN Africa.