Two persons following the same diet do not necessarily achieve the same weight loss results. “There is no universal diet” is a common adage. While the reasons are personalized and beyond measurable by research, one reason is the composition (or profile or enterotype) of the person’s gut microbiota.
Lars Christensen, Ph.D., and his team from the University of Copenhagen, Denmark published their findings in the Journal of Nutrition a few months back. They randomized 75 overweight adults into one of the three diets for 6 weeks: WG wheat, WG rye, or RW (WG, whole grain; RW, refined wheat). Participants were not told to restrict their calories.
As has been well replicated by many studies, those following the high-fiber WG diets lost more weight than the RW diet. More importantly, adults with a higher baseline abundance of Prevotella species in their gut lost 4 pounds while those with lower abundance did not lose any weight, following the same WG diet. Adding more fiber without any calorie restriction can lead to weight loss in individuals, but only in those with a specific gut enterotype.
The same Denmark laboratory also published a similar clinical trial in the International Journal of Obesity in 2018. Herein they showed that adults with high Prevotella abundance lost 7 pounds of body fat on a 26–week New Nordic Diet (high in whole-grain/fiber) than the standard Danish diet. Unfortunately, no fat loss was observed in those with a low baseline abundance of Provetella species on the New Nordic Diet.
In the same year, another study published in the International Journal of Obesity recruited 80 overweight adults for a 24-week, 500-kcal deficit diet (30% fat, 52% carb, 18% protein). They discovered that participants with high gut Prevotella levels at baseline lost more body weight (22 vs 13.5 pounds) and body fat (19.8 vs 11.4 pounds) than those with low Prevotella abundance.
In short, these three studies showed that high-carb, high-fiber diets work better for weight management and fat loss in individuals with Prevotella enterotype but not Bacteroides enterotype.
Dr. Christensen, thus, proposed “microbial enterotypes as promising biomarkers in personalized nutrition for obesity management.” He also suggested that the “key to effective weight loss requires a match between diet and gut microbiota.”
The gut enterotype (or ecosystem) comprises two groups, either a Prevotella- or Bacteroides-dominant. The former is linked to a long-term high-fiber, high-carb diet typically seen in agrarian societies. The Bacteroides enterotype is closely associated with a westernized, high-fat, high-protein diet.
The Ruminococcus, Bifidobacterium, and Enterococcaceaeenterotype enterotypes were classified later, though our understanding of them remains limited.
Gut enterotypes are relatively stable throughout life. They are persistent and don’t easily shift from one enterotype to the other, despite dietary changes. This explains why the high-fibre diet for over 6-months did not change the Prevoltella abundance in those with low Prevotella counts at baseline in the Denmark study above. Of course, exceptions exist and some individuals manage to shift their gut enterotype with dietary practices.
This also explains why the ketogenic diet (higher in fat) reversed obesity in a close friend of mine and kept it off until now (~4 years). The vegetarian diet or the high-carb, low-fat diet did not work. In fact, my friend had been miserable with both those diets for months. Perhaps his gut microbiota resembles the Bacteroides or other enterotypes, with a low abundance of Prevotella species. As Dr. Christensen said, “effective weight loss requires a match between diet and gut microbiota.”
What determines gut enterotypes? There is no straightforward answer. It is probably an equation taking into account multifactorial elements such as genes, sleep patterns, dietary habits, physical activities, mode of infant delivery, childhood antibiotic usage, age, underlying medical conditions and drug usage, and even geographical regions. While some factors are in our control, most don’t.
As Sarkis Mazmanian, professor of microbiology at Cal Tech and one of the pioneers in gut microbiome research puts it: “The assertion that a company can tell you what diet to eat to ‘fix’ your microbiome is just junk. There is no way that anyone has enough information to be able to reshape your microbiome in a meaningful and healthy way, that is tailored to you.
We have no idea what healthy even is, as far as the microbiome is concerned and, since my microbiome configuration is based on my genetics, diet, and life experiences, healthy for me is totally different from healthy for you.”
It made sense that a ‘healthy diet’ is also variable between individuals. It is no wonder that some have a more difficult time controlling their weight and diet than others. And why some diets work magically for a certain subset of the population.
“General dieting schemes often result in failure and disappointment at the personal level and a constant increase in the incidence of obesity and the metabolic pandemic at the population level,” writes Niv Zmora et al. from Weizmann Institute of Science, Israel in their 2018 publication in Nature Gastroenterology & Hepatology Reviews.
They have also made an eye-opening remark that “The evident interrelationships between diet and the microbiota … might reconcile some of the discrepancies that have been troubling nutrition researchers and could explain some of the previously unintelligible variability encountered in the response to diet, at times observed in apparently similar conditions.”
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