Last time I wrote about prebiotics and fibre and satiety/appetite. In 2009 I went to the Nutrition Society Summer meeting at the University of Surrey. The five day conference had concentrated on various aspects of over- and undernutrition. The symposia that I attended were exceptionally interesting and thought provoking. One of the presentations(1) was given by Dr Paul Kelly of Barts and London School of Medicine and Dentistry. He was speaking about the microorganisms in the digestive system and links to diarrhoea in individuals in developing countries. However, he briefly mentioned an animal study that linked the makeup of the bacteria in the digestive system and a propensity to obesity. This got me thinking about whether that link was present in humans. Upon returning home I had a search through the medical databases to see if there was any literature to support these thoughts. Can bacteria in the gut have anything to do with developing excess body weight or obesity? There seems to be a fair amount of recently published interest in the topic of digestive bacterial balance and the links to obesity and overweight (e.g. 2,3,4,5,6). For many years the large intestine was thought only to be important for water absorption and storage of waste. However, the adult human gut contains up to 100 trillion microbial organisms (including bacteria and yeasts) collectively known as the microbiota or microbiome. These gut bacteria seem to have an effect on the entire body and not just the health of the digestive system…..

There has been much written about the link between the bacteria in the digestive system and obesity recently. The human adult gut contains up to 100 trillion microbial organisms and it certainly seems sensible to ensure that these are mainly made up of ‘friendly’ good bacteria. The type of bacteria in the digestive system seems to have an effect on the entire body and not just the health of the gut.   One study (1) found that prebiotic supplementation was associated with reduced appetite sensation after a meal. Prebiotics act as food for the good ‘friendly’ bacteria in the digestive system and previous studies (2) suggest that prebiotics in the diet may reduce our energy and food intake, increase satiety, reduce hunger and appetite and reduce total daily calorie intakes. Prebiotics may also have positive effects on blood sugar balance in the body which can also impact appetite. This research (1) was set up to see whether prebiotic supplements affected the hormones associated with satiety. The study was very small but well designed and provided interesting results. Prebiotic treatment was associated with a three fold reduction in hunger rates and an increase in hormones which are associated with feelings of satiety/fullness.   I would like to stress that obesity is a complex disease involving many factors with no miracle cure and no easy solutions – I am not about to disillusion anyone by inferring that bacterial balance is a major factor and that probiotic or prebiotic supplements are the cure…..