In France, 50% of people are overweight or obese. In its 2022 report, the World Health Organisation sounded the alarm: the prevalence of overweight and obesity is rising steadily – and worryingly – and not a single European Member State looks set to meet the target of halting the rise in obesity by 2025. Obesity is a serious public health problem on a global scale, leading to a host of complications, including an increased risk of cancer – because excess weight increases the likelihood of 13 different types of cancer.
Obesity and the gut microbiota
The gut microbiota is mainly located in the colon (large intestine), and to a lesser extent in the small intestine. It is spread throughout the interior of the digestive tract and in the mucus, a protective layer on the inner lining of the digestive tract, the intestinal epithelium. One of its vital functions is to act as a barrier against pathogens. The mucus prevents pathogens of dietary origin (like heavy metals) or of microbial origin from passing through the epithelium and spreading throughout the body via the bloodstream. With intestinal dysbiosis, our bacteria no longer produce sufficient mucus and the junctions between intestinal cells become distended. The intestine becomes hyperpermeable (porous), allowing toxic waste to enter the bloodstream, which causes various health problems like obesity.
The gut microbiota of obese people is less varied: 15% of the European population have a poor gut microbiota, but this figure rises to 25% in cases of overweight or obesity. It can even exceed 50% in cases of massive obesity or type 2 diabetes. The intestinal flora of obese people also contains fewer good bacteria, with a decrease in lactobacilli and bifidobacteria, the “friendly” bacteria that reduce inflammation and the formation of fatty tissue.Bacteroidetes and firmicutes are two large families of bacteria that make up over 90% of the gut microbiota. There are over 250 kinds of firmicutes, including lactobacilli, streptococci, enterococci and clostridia.
Bacteroidetes consist of some 20 different types. In cases of obesity, there is an excess of firmicutes, which have a greater capacity to digest complex carbohydrates. As there are more of them, they extract more calories from food than bacteroidetes do, which leads to an increase in body fat. In other words, with the same daily calorie intake, the energy intake will be greater in people whose gut microbiota is unbalanced.
In addition, with intestinal dysbiosis, the gut-brain axis is disturbed, and this imbalance disrupts the reward messages sent to the brain, making us feel a pleasure deficit, so that we consume more “comfort” foods (too sweet, too fatty or too salty).
Microbiotic medicine to combat overweight and obesity
Alongside diet, physical activity and bariatric surgery, a new medical means of combating obesity has emerged: modulating the gut microbiota using prebiotics and probiotics.
Prebiotics
These plant fibres, which we do not digest, are food for our friendly intestinal bacteria and help them to multiply. They are found in vegetables, fruit, legumes and wholegrain cereals, as well as seeds like flax and chia.
Five foods have prebiotic concentrations ranging from 100 to 240 mg/g of prebiotics:
- dandelion leaves (which can be eaten as a salad or cooked);
- Jerusalem artichokes
- garlic
- leeks
- onions cooked or raw.
Probiotics
Probiotics are live micro-organisms that have beneficial effects on health when ingested in sufficient quantities. They can be found in food – yoghurt, sourdough bread, lacto-fermented vegetables, kefir, kombucha, etc. – or in capsule form with different strains indicated according to the pathology to be treated: obesity, irritable bowel syndrome, stress, etc.
Several probiotic strains have proved effective in treating obesity and form an integral part of microbiotic medicine. One that stands out is Hafnia alvei 4597, a precision probiotic that acts on the satiety hormone leptin. A recent multi-centre randomised placebo-controlled clinical study (the essential clinical study) demonstrated the anti-obesity effects of the strain called Hafnia alvei 4597: it increases the feeling of satiety because it acts on leptin, the hormone that provokes this feeling. As this not only leads to a decrease in weight and hip circumference, but also has positive effects on glycemia and insulin resistance, it is of particular interest for obese and diabetic patients.
A meta-analysis including all randomised controlled trials carried out between August 2014 and December 2020 (32 studies involving 1,818 subjects) compared probiotics with a placebo in overweight or obese adults. Compared with a placebo, probiotic intake led to a reduction in body mass index (BMI), body fat percentage, blood triglycerides, total cholesterol, blood sugar levels and fasting insulin levels. This meta-analysis thus confirmed the efficacy of probiotics in improving anthropometric markers and lipid and glycemic profiles in overweight or obese people.
Probiotics in capsules
Physical activity
Physical activity also has an effect on the gut microbiota. The fermentation of carbohydrates in the colon leads to the production of three short-chain fatty acids (acetate, propionate, butyrate) known as postbiotics. These postbiotics perform multiple actions, including fighting inflammation and cancers, but they also play a role in balancing glycemia (the blood sugar level) and regulating appetite. This explains the benefits of physical activity, whose effect goes far beyond calorie loss through its action on the gut microbiota.
Conclusion
Since monotrophic, high-protein and ketogenic diets have been shown to be largely ineffective in the medium and long term, it is essential to rebalance the gut microbiota if a person wants to lose weight.
The threefold method of the Mediterranean diet 2.0 + physical activity + appropriate probiotics can have a favourable effect on the gut microbiota synergistically, and thus effectively combat overweight and obesity.
This article is excerpted from one of the files of the PRO BTP Health Observatory: Obesity. You can find other resources related to this study file here.
PRO BTP created the Health Observatory to support those who wish to take an active role in their well-being: understanding, preventing, and taking action on their health in everyday life.
Chronicles, interviews, podcasts, videos... In partnership with a network of recognized experts and major national media outlets, the observatory provides you with key insights, practical advice, and concrete, innovative solutions, addressing a significant health topic each month.
Selected for their relevance to the French public, the topics are rigorously covered by a scientific committee, composed of recognized health experts and professionals, and specialized journalists, to provide you with reliable and useful information for your daily life.
