Liquid Supplements Seem More Effective As Snacks Than With Meals
The study, which is described in the May American Journal of Clinical Nutrition, also found that younger people regained their appetite sooner than elderly people, especially after drinking a high-fat or high-protein supplement.
On average, it took 94 minutes for the 15 study participants who were age 70 or older to become hungry after drinking a high-fat supplement, but 70 minutes for the 15 participants who were 2040 years old. Seniors became hungry an average of 72 minutes after drinking a high-protein supplement, and younger study participants were hungry about 64 minutes after drinking the supplement.
After drinking a supplement, participants of all ages ate smaller portions of a test meal offered five minutes later than of a comparable meal that was delayed by at least an hour. On average, study participants consumed 497 kilocalories worth of fat, protein, and carbohydrate when the meal began five minutes after intake of the supplement. Energy consumption increased to 679 kilocalories when the meal was offered at least an hour after the supplement.
The study team suggested that elderly patients can increase their energy intake by drinking a liquid dietary supplement between meals and then waiting at least an hour to eat the meal.
All study enrollees were healthy adults from the St. Louis area who normally ate three or more regularly spaced meals each day and took no medications. On average, the seniors were 78 years old and the young adults 29.
For the first part of the study, each enrollee fasted overnight and then drank 300 mL of water or a 300-kilocalorie high-protein, high-carbohydrate, or high-fat nutritional supplement. Five minutes after drinking the supplement, the study participants ate as many small sandwiches as they wanted until they no longer felt hungry. Each participant completed all four liquid-supplement "preload" portions of the study in random order.
During the second part of the study, the 300-kilocalorie supplement or water preload preceded the meal by at least an hour. After the hour elapsed, the participants were given small sandwiches on request and told to eat until they felt sated.
Because the high-fat supplement suppressed seniors' appetite for a particularly long period, the research team suggested that supplements with less fat may encourage seniors to consume more food energy overall. The researchers described their findings as preliminary but worthy of additional study.