News archive 2009

Why low GI makes you feel full

18 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.’

Blood samples

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.

For more information: please contact the Society for Endocrinology press office:
Rebecca Ramsden, Public & Media Relations Assistant
Mobile:+44 (0)7561 945 676      
Tel: +44 (0)1454 642 252
Email: rebecca.ramsden@endocrinology.org    

King’s College London
King’s College London is one of the top 25 universities in the world (Times Higher Education 2008) and the fourth oldest in England. A research-led university based in the heart of London, King’s has 19,700 students from more than 150 countries, and 5,400 employees. An investment of over £500 million has been made in the redevelopment of its estate in recent years.

King’s has an outstanding reputation for providing world-class teaching and cutting-edge research. In the 2008 Research Assessment Exercise for British universities, 23 departments were ranked in the top quartile of British universities; over half of our academic staff work in departments that are in the top 10 per cent in the UK in their field and can thus be classed as world leading. The College is in the top group of UK universities for research earnings and has an overall annual income of approximately £450 million.

King’s has a particularly distinguished reputation in the humanities, law, the sciences (including a wide range of health areas such as psychiatry, medicine and dentistry) and social sciences including international affairs. It has played a major role in many of the advances that have shaped modern life, such as the discovery of the structure of DNA and research that led to the development of radio, television, mobile phones and radar. It is the largest centre for the education of healthcare professionals in Europe; no university has more Medical Research Council Centres.

King's College London and Guy's and St Thomas', King's College Hospital and South London and Maudsley NHS Foundation Trusts are part of King’s Health Partners. King’s Health Partners Academic Health Sciences Centre (AHSC) is a pioneering global collaboration between one of the world’s leading research-led universities and three of London’s most successful NHS Foundation Trusts, including leading teaching hospitals and comprehensive mental health services.

The driving purpose of King's Health Partners is to continually seek and bring about swifter and more effective improvements in health and well-being for patients in London and people everywhere. Combining the best of basic and translational research, clinical excellence and world-class teaching to deliver groundbreaking advances in physical and mental healthcare.
For more information, visit :www.kingshealthpartners.org

Further information
Alexandra Bevis, Communications Officer,
Public Relations Department, King's College London
Email: alex.bevis@kcl.ac.uk Tel: 020 7848 3202

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