News archive 2009
Why low GI makes you feel full18 Mar 2009, PR 55/09
Eating a low GI (glycaemic index) meal, such as a bowl of porridge in the morning, will keep you feeling fuller for longer, King’s scientists have discovered, in what could be the key to how the GI diet works.
Researchers from the Department of Nutrition and Dietetics have found that low GI (glycaemic index) meals increase gut hormone production which leads to the suppression of appetite and the feeling of fullness. This research presented yesterday at the annual Society for Endocrinology BES meeting is the first study to provide clues as to how a low GI meal produces satiety.
GI is a ranking assigned to carbohydrates according to their effect on the body’s blood sugar levels. A low GI meal takes longer to digest and releases sugar into the bloodstream more slowly than a high GI meal. A low GI diet is known to cause reduced appetite(1) but the mechanisms behind this have so far remained unknown. To address this Dr Tony Leeds, Senior Lecturer in Nutrition and Dietetics, and Reza Norouzy at King’s College London looked at the effects of a single low versus high GI meal on gut hormone levels in 12 healthy volunteers.
Dr Reza Norouzy said: ‘Our results show for the first time the direct effect of a single GI meal on gut hormone levels. We already know that the hormone glucagon-like peptide 1 (GLP-1) and a low GI meal independently lead to suppression of appetite. This study builds on these findings by providing a physiological mechanism to explain how a low GI meal makes you feel fuller than a high GI meal. GLP-1 is one of the most potent hormones for suppressing appetite.
‘Our results suggest that low GI meals lead to a feeling of fullness because of increased levels of GLP-1 in the bloodstream. This is an exciting result which provides further clues about how our appetite is regulated, and offers an insight into how a low GI diet produces satiety. This is a preliminary study and we now need to expand these findings and look at the effects of low versus high GI meals in a larger cohort of people.’
Professor Peter Emery, Head of Department of Nutrition and Dietetics, and one of the paper’s author’s comments: ‘These are important findings. The role of gut hormones in appetite and satiety is a hot topic at present as we search for ways of controlling the rising tide of obesity. The findings of this study are an important first step in understanding how low GI foods can help to address issues of weight control and what part they should play in a balanced diet.’
Each participant ate an identical medium GI meal for dinner, fasted overnight, and was given either a low (46) or high (66) GI meal for breakfast. Blood samples were then taken every 30 minutes for 150 minutes, and levels of the gut hormone GLP-1 and insulin measured. GLP-1 is a hormone produced by the gut that has been shown to cause a feeling of fullness and suppression of appetite(2).
Volunteers who ate a low GI breakfast had 20 per cent higher blood plasma levels of GLP-1 and 38 per cent lower levels of insulin compared to those who had consumed a high GI breakfast. These results show for the first time that eating a low GI meal increases GLP-1 production and suggest a physiological mechanism as to why a low GI meal makes you feel fuller than a high GI meal.
[Image from iStockphoto]
Notes to editors
1 Pal S, Lim S. The effect of a low glycaemic index breakfast on blood glucose, insulin, lipid profiles, blood pressure, body weight, body composition and satiety in obese and overweight individuals: a pilot study. J Am Coll Nutr. 2008; 27(3):387-93.
2 Naslund E, Barkeling B. Energy intake and appetite are suppressed by glucagon-like peptide-1 (GLP-1) in obese men. Int J Obes Relat Metab Disord. 1999; 23(3):304-11.
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