Obesity arises when the energy intake from what we eat is greater than the energy we consume. However, the ability to maintain an energy balance varies between individuals. We now know that several contributory factors are involved, of which the best known are genetic predisposition and lifestyle (diet and exercise). The bacteria in gut microbiota (see fact box 1) are thought to play an important role in both the development of obesity and future diseases.
Collection of faeces samples
As a part of her thesis project, Louise Brunkwall was involved in starting up the Malmö Offspring Study (MOS) in 2013. The study monitors several generations of people, accumulates information on health and diet, and collects faeces samples. The aim is to have 5000–6000 participants by the end of 2020.
The initial results from the study show that there may be a link between obesity measured by BMI (see fact box 2) and gut microbiota.
“We have seen a link between a healthy eating pattern and a reduced risk of prediabetes – a preliminary stage of type 2 diabetes – which possibly goes via a bacterium in the gut, which helps to break down fibre. This could show that a healthy eating pattern may contribute to the growth of good bacteria with positive health effects.”
Overall diet must be taken into account
The thesis also includes two projects in which Louise Brunkwall studied genetic predisposition as well as lifestyle linked to eating patterns.
“We found that those who have more risk genes for overweight and drank soft drinks ran a greater risk of becoming overweight than those with fewer risk genes or those who drank fewer soft drinks”, says Louise Brunkwall.
However, it was shown that in general those who consume lots of soft drinks (more than one can per day) also had poorer eating habits than those who did not consume soft drinks at all or only in moderation.
“The conclusion from this study was that perhaps it’s not as simple as soft drinks being the sole cause of a considerably heightened risk of overweight, but the diet as a whole. It’s therefore important to take the overall diet into account when studying individual foods.”
A high intake of sugar-sweetened drinks, artificially sweetened drinks and coffee could be linked to individuals with a high BMI and lower level of education, whereas a higher intake of juice and tea was linked to a lower BMI and higher level of education.
“We could also see that those who drank highly sweetened drinks ate less of the food that is commonly associated with good health such as fruit, vegetables, yoghurt and fish, whereas those who drank a lot of juice and tea ate a lot of this type of food.”
"Bacteria is affected by everything"
Louise Brunkwall is critical of books and blogs that give the impression of “knowing” and which provide advice and recipes said to have a scientific basis. “Most of the studies that you can refer to are very small or conducted on animals. Many studies have looked at extreme groups or examined the effects of only eating cheese for three days, for example. It can be seen that bacteria are affected by pretty much everything.”
No one has such a narrow diet and everyone lives in a context, so understanding what is good or bad necessitates the study of thousands of people.
A “good gut microbiota”
It is not really known at present what constitutes a “good gut microbiota”.
“Gut microbiota has so many aspects. We are only looking at some form of end product, we don’t know what happens further up in the intestinal tract”, says Louise Brunkwall.
So, what is the conclusion of the thesis project?
“I believe that a greater understanding and knowledge of gut microbiota can highlight the importance of diet and possibly contribute to more individually tailored healthcare. I don’t think this will change the current recommendations, but it may boost our motivation to adopt a better diet if we know why it’s good”, concludes Louise Brunkwall.
Footnote: Louise Brunkwall was awarded her doctoral degree at Lund University in June 2019.
Link to thesis: Obesity; with a focus on diet quality and gut microbiota
Facts/ Gut microbiota
Gut microbiota includes bacteria, archaea (archeabacteria), fungi, viruses etc. that live in the human gut. Bacteria account for one kilo of an adult person’s body weight.
Studies have shown that a fibre-rich diet is good, as bacteria that break down fibre produce short chain fatty acids that are important for the body’s metabolism. Likewise, the bacteria that produce mucus have been shown to build up the inside of the gut so that it does not release substances into the bloodstream and cause damage in the form of autoimmune diseases.
Facts/ Obesity
A body mass index (BMI) over 30 indicates obesity. BMI is a measurement based on a person’s weight and height. Obesity is a risk factor for type 2 diabetes, which is estimated to cause one million deaths each year. In addition to type 2 diabetes, obesity is a risk factor in cardiovascular disease, several forms of cancer and mental illness.
