Some people really struggle to lose their extra weight, despite eating a strict and healthy diet, consuming no carbohydrates or sugars, and doing plenty of exercise. The intestinal flora can be the cause of this. Scientific studies have shown that those who are overweight have a totally different distribution of gut bacteria than those who are a healthy weight. Gut bacteria can be split into two groups, bacteroidetes and firmicutes, which should, ideally, be of equal amounts in the gut. In overweight people this balance tends to be shifted in favour of the firmicutes. Firmicutes have the ability to extract as many calories as possible from food – they can even convert dietary fibre, which is not normally digestible, into calories. As a result, people who have more fermicutes in their intestine tend to absorb more calories even though they may not eat more. People who weigh much less tend to have a higher percentage of bacteroidetes and, therefore, a lower percentage of firmicutes, A simple test allows us to examine whether someone utilises their food well and, as a result, is absorbing the correct amount of calories. Verisana offers a stool test which can determine the balance between firmicutes and bacteroidetes (adiposity index). The ratio between both types of bacteria can serve as a basis for a change in diet and the administration of probiotics.