TWO ways in which dieters try to make themselves feel full without stuffing themselves with food have been backed up by separate research teams.
One effect of overeating is to disrupt the action of appetite-suppressing hormones, leading people to eat even more. The role of exercise in restoring the hormones' action, and so helping people feel full, has been investigated by a team from the State University of Campinas, Brazil.
The hormones leptin and insulin both act to control appetite by binding to receptors in a brain region called the hypothalamus, initiating the "I'm full" feeling. Overeating generates excess fatty acids that inflame part of the hypothalamus, decreasing the uptake of these hormones.
After exercising lean and obese rats, the team observed their eating habits over the following 12 hours. Obese rats ate about 25 per cent less than they had before their workout but no change was seen in the lean rats' eating habits (PLoS Biology, DOI: 10.1371/journal.pbio.1000465).
The team also found that, after exercising, the obese rats' brains contained dramatically increased levels of anti-inflammatory proteins that are produced during muscle contractions, compared with the lean rats. Co-author José Carvalheira reasons that exercise didn't affect the lean animals' appetite because their hypothalamus was not inflamed.
If exercise doesn't appeal, you could try drinking a few glasses of water before eating a meal. At this week's meeting of the American Chemical Society in Boston, Brenda Davy from Virginia Tech in Blacksburg announced the results of the first clinical trial into this practice. She and her colleagues found that over 12 weeks, adults on a low-calorie diet who drank two glasses of water before meals lost 7 kilograms, while non-water-drinkers lost 5 kilograms.
After the end of the low-calorie diet, water drinkers who continued the practice for 12 months while eating well were better at keeping the weight off. "This is an important finding," says Davy, as keeping off lost weight is a major challenge for people who have been dieting.