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27.10.2008

Want to lose weight? Blend your protein shakes for longer

If you use protein shakes and need to lose weight, then researchers at Pennsylvania State University have a tip for you: keep the blender on for longer when making a shake so that its volume increases. If you drink a whipped shake, you'll eat less the rest of the day.

Study
The researchers were not actually doing tests with protein shakes, but with the carbohydrate bombs you can get at treatment centres for fat addicts. But it doesn't matter – the researchers' findings apply to protein shakes as well.

The researchers gave a group of almost thirty men a shake to drink half an hour before lunch. The shakes had a volume of 300 mm, 450 mm or 600 mm, but all contained the same amount of kilocalories. The difference between them was the amount of time they had been in the blender. The longer they had been blended, the more air bubbles they contained, and the greater the volume of the shake.

After that the men had lunch and – at the end of the day – dinner. The men were allowed to eat as much as they wanted.

Results
The shakes contained five hundred kilocalories. The men who drank a shake therefore had a higher energy intake for the whole day than those who did not drink a shake. Nevertheless, the men that had the shake that had been blended longest ate twelve percent less kilocalories at lunch.

The appetite reducing effect of the high-volume protein shakes had disappeared by the evening, when the subjects ate dinner.

Mechanism
The researchers have offered two possible explanations for the effect. One is that the whipped shake makes the stomach feel fuller. The other is that it takes longer to consume a whipped shake. That might have led to a greater feeling of satiety.

Sources:
Am J Clin Nutr. 2000 Aug;72(2):361-8.