Acute effects of whey protein on energy intake, appetite and gastric emptying in younger and older, obese men

Background: Obesity is increasingly prevalent in older adults. Increasing dietary protein is a weight-management strategy in younger adults, but its efficacy in obese, older individuals is unclear. We previously showed a 30 g whey drink slowed gastric emptying more and suppressed energy intake less in older vs younger non-obese men. This study evaluated the effect of a 30 g whey drink on energy intake, gastric emptying (GE), and glycaemia in obese younger and older men. Methods: In a randomized, double-blind, cross-over study, 10 younger (27 ± 2 y; BMI 36 ± 2 kg/m²) and 10 older (72 ± 1 y; BMI 33 ± 1 kg/m²) obese men ingested a 30 g whey protein drink (120 kcal) or control (~2 kcal) after an overnight fast. GE (antral area, 2D ultrasound) and blood glucose were measured for 180 min. At 180 min, subjects consumed an ad libitum buffet meal. Results: Older subjects ate ~20% less than younger subjects (age effect P=0.16). Whey protein did not affect subsequent energy intake vs control in younger (−3 ± 8%) or older (−2 ± 8%) men (protein effect P=0.46; interaction P=0.84). Whey protein slowed GE similarly in both age groups (T50: young control 25 ± 5 min vs protein 40 ± 7 min; older control 16 ± 5 min vs protein 50 ± 8 min; protein effect P=0.001). Conclusions: Obesity may blunt or abolish the age-related suppression of energy intake by whey protein.

Avneet Oberoi, Caroline Giezenaar, Caroline Jensen, Kylie Lange, Trygve Hausken, Karen L. Jones, Michael Horowitz, Ian Chapman, Stijn Soenen