Insatiable Appetite? Think of Bacteria!
The hunger phenomenon and the numerous micro-organisms that make up the microbiota are two subjects that fascinate humans and that are in fact … intimately related! Today there is reason to believe that our eating habits are partly dictated by our intestinal flora. Conventional opinion often associates junk food and malnutrition to a simple lack of will1. The attempt to resist cravings for high fat and sweet foods is a daily struggle for many people1. We now realize that various factors increase appetite, we can name among others:
- our individual probiotic profile, particularly in case of dysbiosis;
- the conditions surrounding meals, when the swallowing speed is reduced and the eating routine is unstable;
- circadian influences, especially for those who work night shifts;
- genetic particularities2.
A suboptimal diet sooner or later contributes to health problems such as obesity, diabetes, cardiovascular disease and even cancer1. Epidemiological data indicate higher rates of cancer in obese women compared to those with a healthy weight3. In an ideal world, happy eaters would consume a majority of vegetables and fresh fruits, lean animal protein, drinks that are not too sweet, and processed and refined foods only occasionally … and always in reasonable serving sizes3. Most of us know what foods should be part of an optimal diet, but it’s not always so easy to implement it in our daily routine!
Probiotics in all of this?
Recent advances in our understanding of the human microbiome have raised a lot of enthusiasm. Research suggests that the vagus nerve, the only cranial nerve to extend beyond the head and neck, would regulate dietary habits as well as body weight. Microbes can exert their influence on the host via key hormones like dopamine and serotonin1. Moreover, the good bacteria in our body produce beneficial lactic acid, in addition to secreting immunomodulatory substances (histamine among others) as well as calming substances (GABA or amino-butyric acid for example)1. It has been shown that the presence of butyrate in the blood, a substance produced by probiotics, has profound effects on the central nervous system and mood in mice1.
Animal studies have shown that aseptic mice have more fat taste receptors on their tongue and more sugar receptors in their digestive tract, which was not the case for mice with normal bacterial colonization1. These small bacteria-free animals also had lower levels of leptin, cholecystokinin (CKK), and other satiety-promoting agents1. People who have a fondness for chocolate have different microbial samples in their urine than people who are indifferent to chocolate, despite eating identical diets. Microbes could, therefore, explain many things!
In a Quebec supplementation study conducted at Laval University, administering a Lactobacillus rhamnosus probiotic for 12 weeks to subjects who wished to lose weight resulted in a significant reduction in appetite in most subjects, especially women4. That being said, it can be inferred that the addition of probiotics in the form of a dietary supplement tends to reduce caloric intake. According to the hypothesis that a greater intestinal bacterial diversity can promote positive effects on appetite management, and improvement of nutritional behaviours.
Let it be said!
The obesity epidemic is closely linked to major changes in food production practices and consumer trends around the Globe … unfortunately, we’re all on the same boat. Given the complexity of nutrition and the difficulty of making changes to one’s dietary habits, statistics do not improve much over time. All possible solutions must be considered to overcome this scourge.
Did you know?
Under the influence of stress, some bacteria actually produce a CLPB enzyme which is studied by many researchers for its astonishing feature: it mimics the effect of a satiety hormone, melanotropin. Scientists go as far as to believe that this could explain the loss of appetite in certain eating disorders such as anorexia nervosa5.
1Alcock J, Maley CC et Aktipis CA.
Is eating behavior manipulated bythe gastrointestinal microbiota? Evolutionary pressures and potential mechanisms. Bioessays. 2014 ; 36 (10) : 940-949.
2Feinle-Bisset C. Modulation of hunger and satiety : hormones and diet. Curr Opin Clin Nutr Metab Care. 2014 ; 17 (5) : 458-464.
3Pace LA et Crowe SE. Complex Relationships Between Food, Diet, and the Microbiome. Gastroenterol Clin North Am. 2016 ; 45 (2) : 253-265.
4Université Laval. Certains probiotiques pourraient aider les femmes à perdre du poids. [Site web]. Consulté le 20 août 2018. https://www.ulaval.ca/notre-universite/salle-de-presse/communiques-de-presse/details/article/certains-probiotiques-pourraient-aider-les-femmes-a-perdre-du-poids.html
5Science et Avenir (France). La flore intestinale influence notre appétit. [Site web]. Consulté le 20 août 2018.