The findings from this study could further aid the creation of ‘intelligent’ foods that control and release the energy available. Considering that control of energy intake is vital to energy balance, understanding the appetite control system is important to combat the obesity epidemic.
Sports nutrition in particular has taken the lead in developing products that focus on meeting recommendations for protein amounts and timed delivery.
Findings from this research agree with a general hierarchy of macronutrients’ satiating power in which protein is considered more satiating than carbohydrates and carbohydrates more satiating than fat.
However, study design has varied the different preload time intervals, sources of macronutrients, energy density, volume, and palatability as well as subject characteristics making it difficult to pinpoint the optimum dose or energy percentage needed to observe the macronutrients’ effects on satiety.
Satiety study details
The study, which took place at the Lund University in Sweden, enrolled 23 men and 17 women aged between 20 and 50 years old. Each morning, subjects were asked visit the laboratory and report on the meal they consumed the night before.
During each of these visits, subjects drank an experimental beverage containing a specific ratio of protein, carbohydrate, and fat. These beverages provided the same level of calories and were consumed in equal volumes.
Several hours later, subjects were offered a lunch meal of tortellini with tomato sauce and cheese and asked to consume as much as they liked. The researchers then investigated how each "preload" beverage influenced feelings of fullness, subsequent lunch consumption, and blood levels of several hormones and metabolites.
The results indicated consumption of the lunch meal was 12% lower after intake of the high-protein (40%) preload beverage than after intake of the low-protein (9%) preload beverage. In other words, regardless of the preload beverage's fat and carbohydrate contents, consuming a high-protein version suppressed appetite the most.
The researchers found most of the appetite ratings tended to be suppressed (13%) with increasing protein content of the preloads. Carbohydrate produced greater increases in fullness and postprandial responses of glucose and insulin than did protein and fat.
The study believed protein was the most influential macronutrient for the lunch meal consumption because both beverages with high protein content significantly suppressed prospective consumption compared with the beverage with low protein content.
However, there were no differences in the other appetite sensations between the beverages which had differing carbohydrate to fat ratios. The researchers believed that carbohydrates worked together with protein to generate the appetite sensations.
Peptide activation
The study also found consuming the high-protein treatment also lowered blood glucose and raised glucagon-like peptide 1 concentrations.
“This is especially interesting because glucagon-like peptide 1 is known to suppress appetite,” said lead researcher, Dr Anestis Dougkas from Lund University.
“These effects were generally opposite for the high-fat preload (suggesting that consuming fatty foods impact appetite less than protein and carbohydrate) and the same in men and women.”
Although there were no differences in the amount of food consumed at lunch, the researchers concluded that "adjusting the nutritional profile of a meal, especially replacing fat with protein, could make dieting more endurable."
Source: Journal of Nutrition
Published online ahead of print, doi: 10.3945/jn.115.217224
“Protein-Enriched Liquid Preloads Varying in Macronutrient Content Modulate Appetite and Appetite-Regulating Hormones in Healthy Adults.”
Authors: Anestis Dougkas, Elin Ostman