Consuming whey protein before or with breakfast improves postprandial glycaemia in obese men

Aims: To examine whether whey protein intake before, during or after a breakfast meal influences postprandial glycaemia and subjective appetite responses in obese males. Methods: Ten centrally-obese males, free from metabolic disease (age 35±7 years, waist circumference 119.2±9.1 cm, body mass index 34.5±3.6 kg/m2, fasting plasma glucose 4.9±0.3 mmol/l) completed four trials in a randomised counterbalanced fashion. Participants arrived at 08:30am following a ~12 h fast and consumed a standardised breakfast meal (67% energy from carbohydrate, 468 kcal) on each occasion. Whey protein isolate (20 g) was consumed either 15 min prior to (PRE), during (DUR) or 15 min post (POST) breakfast, or was omitted (CON). Capillary blood glucose and subjective appetite responses were determined for 180 min following ingestion of the test breakfast. Results: Postprandial glucose area under the curve (AUC) was lower for 60 min following breakfast consumption under PRE and DUR compared to CON (AUC 0-60s, PRE 361±7; DUR 380±15 vs CON 432±9 mmol/l/min, p <0.007), with no differences observed when compared to POST (403±13 mmol/l/min, p > 0.05). AUC for the whole 180 min post breakfast was similar across trials (p > 0.05). Peak postprandial glucose was significantly lower under PRE and DUR than under CON (PRE 6.9±0.1; DUR 7.4±0.3 vs CON 8.4±0.2 mmol/l, p <0.012), with PRE also significantly lower than POST (POST 8.1±0.2 mmol/l, p = 0.004). Subjective ratings of hunger and fullness did not differ between trials (p > 0.05). Conclusions: Consuming whey protein before or with breakfast reduces acute postprandial glycaemia in obese males. The timing of whey protein consumption has little effect on postprandial appetite sensations.