Intestinal flora, important in obesity

The intestinal flora of laboratory animals and people with overweight and obesity appears to be significantly different in composition than that of their lean controls. This intestinal flora ensures better extraction of energy from food and greater storage of calories in fat tissue. This makes it all the more difficult for those who are overweight to lose weight.

Functions of intestinal flora

The intestinal flora fulfills a number of essential functions, including supporting digestion and the absorption of nutrients, stimulating intestinal peristalsis, breaking down toxic and carcinogenic substances in food, the production of vitamins and fatty acids (fuel for the intestinal epithelium) and the defense against pathogens. Intestinal bacteria ferment indigestible food remains (dietary fibres) and extract (extra) energy from them.

Development of intestinal flora

A child receives the first bacteria through the birth canal that will populate the gastrointestinal tract. The microorganisms with which the child comes into contact after birth stimulate the development of the intestinal immune system and determine the final composition of the intestinal flora. From about the age of 2, the intestinal flora has a stable, highly individual composition and remains relatively constant for the rest of life. It is possible that the balance between the different micro-organisms shifts (such as between bacteroidetes and firmicutes); (potentially) pathogenic bacteria and fungi can also gain the upper hand (dysbiosis, gastrointestinal infection). The diet is a factor that can change the composition of the intestinal flora for a long time.

Balance Bacteroidetes and Firmicutes

Research has shown that the bacterial flora of fat laboratory animals (mice) and humans consists of fewer Bacteroidetes and more Firmicutes compared to lean controls. Scientists transferred the intestinal flora of obese mice to mice without intestinal flora and to lean mice, with the result that these mice quickly became obese even though they stopped eating. This suggests that changes in intestinal flora at the stem level have a major influence on the efficiency with which food is converted into energy. Firmicutes bacteria may obtain more energy from (residual) food than Bacteroides.
When obese laboratory animals and humans lose weight, the intestinal flora changes accordingly and the relative proportion of Bacteroides increases (and that of Firmicutes decreases) by 3% to 15%, depending on the percentage of weight loss. The composition of the intestinal flora and body weight are therefore clearly correlated.

Energy regulation by intestinal bacteria

Intestinal bacteria influence energy balance in different ways. They ferment indigestible polysaccharides into substances usable by the body, increase the intestinal absorption of monosaccharides and short-chain fatty acids, stimulate lipogenesis in the liver and regulate (host) genes that regulate fat deposition in adipocytes. Normal mice with intestinal flora have 40% more body fat than mice without intestinal flora, even though they eat the same. Transferring the intestinal flora to the microbe-free mice increased body weight by 60% in 2 weeks and caused insulin resistance, fat cell hypertrophy and increases in leptin and glucose levels.

Intestinal flora influences weight

In a prospective study, a group of children were followed from birth to age 7. At the ages of 6 and 12 months, the feces were examined for bacteria. Children who were slim at age 7 had high levels of bifidobacteria and low levels of Staphylococcus aureus bacteria in their feces as babies compared to children who were overweight or obese. This suggests that an unfavorable composition of the intestinal flora predisposes to overweight and obesity.

Chronic systemic inflammation

Insulin resistance is associated with low-grade chronic systemic inflammation. The intestinal flora can play an important role in this. Gram-negative bacteria in the intestinal flora produce LPS (lipopolysaccharide), which has a pro-inflammatory activity and can contribute to the development of obesity, metabolic syndrome and type 2 diabetes. Animal research has shown that a high-fat diet increases the production of LPS by intestinal bacteria. (endotoxemia). LPS attaches to immune cells and stimulates the production of pro-inflammatory cytokines (particularly TNF-α, IL-1, IL6 and plasminogen activator inhibitor 1), which significantly contributes to insulin resistance.8 An antibiotic specifically targeted against gram-negative
microorganisms led to a decrease in the expression of LPS and reduced fatty liver disease in a human study.1 Higher LPS levels are also found in patients with type 2 diabetes than in controls without diabetes. Recently, human research has shown that a high-calorie diet causes an increase in the LPS plasma level. A high-fat diet causes a much greater increase in the LPS level than a high-carbohydrate diet, probably because fats ensure a greater absorption of bacterial LPS from the intestinal lumen into the blood.

Antibiotics, prebiotics and probiotics

The question is to what extent the use of antibiotics, pre- and probiotics contributes to the development of an (anti)obesogenic intestinal flora. The intake of prebiotics seems beneficial. Prebiotics such as fructo-oligosaccharides (FOS) stimulate the growth of beneficial bacteria such as Bididobacteria and Lactobacilli. There are indications that FOS ensures lower energy intake and better satiety after eating, so that the risk of obesity decreases. Increase in the number of bifidobacteria through the use of FOS is associated with a decrease in the production of LPS by the intestinal flora and an improvement in glucose tolerance. It is not yet clear whether existing probiotics (particularly probiotics with bifidobacteria) can promote anti-obesogenic intestinal flora.

In any case, a diet that regulates intestinal flora can also help you keep your weight under better control. Plants that contain a lot of FOS can help with this. It is therefore not without reason that dandelion, Jerusalem artichoke and artichoke, plants with a lot of FOS, are recommended in herbal medicine against obesity.