Recent studies suggest that manipulating the composition of the gut microbiota may prevent weight gain or facilitate weight loss in humans
Today, 1 out of 4 Malaysian school children are either overweight or obese while obese and overweight Malaysians make up 17.7% and 30% of the population respectively, according to the 2015 National Health and Morbidity Survey. If this trend continues, most of our adult population will soon be out of shape and prone to various chronic non-communicable diseases (e.g. coronary artery disease, fatty liver, diabetes, kidney disease and digestive tract cancers).
We know by now that obesity and type 2 diabetes are risk factors for many diseases and are influenced both by genes and environmental factors, in particular lifestyle. But what's interesting is that recently, researchers have discovered that the genes of our gut microbiota may also play an important role. This revelation could provide a potential solution to the recent and growing obesity epidemic now trending worldwide.
Microbes For Health, Really?
This comes as no surprise since the gut microbiota and its role in both health and disease has been the subject of extensive research, establishing its involvement in human metabolism, nutrition, physiology, and immune function. Imbalances between bad and good gut microbiota, so called 'dysbiosis' on the other hand, have been linked with various gastrointestinal disorders such as inflammatory bowel disease (IBD), irritable bowel syndrome (IBS) and even digestive tract cancers, in particular colorectal cancer.
According to Assoc Prof Dr Raja Affendi Raja Ali, "Our gut microbiota is linked heavily with our body, where both coexist together in a symbiotic relationship where microbes have evolved together with human kind – one is influenced by the other." Assoc Prof Dr Raja Affendi, who is a Physician and Consultant Gastroenterologist at Hospital Canselor Tuanku Muhriz, Universiti Kebangsaan Malaysia (UKM) Medical Centre, is himself, working on the clinical trial and research to investigate the effects of lactobacillus-based cultured milk drinks among irritable bowel syndrome patients with predominant symptoms of constipation.
Gut Microbiome Link To Weight Gain
Besides factors such as birth by caesarean section, breastfeeding, introduction of solid foods to infants, and the frequent use of antibiotics by the mother or infant as well as the way we live our lives today have also directly and indirectly affected the composition of our 'good and bad gut microbiota friends' inside our digestive tract. As assoc Prof Dr Raja Affendi explains, "poor dietary habits, lack of exercise, high stress levels and pollution have all wreaked havoc on our gut ecosystem causing an imbalance of the gut microbiota".
The imbalance of the gut microbiota proved to be among the key factors of weight gain in many studies. The link between microbes in obesity was shown in one landmark animal study by Backhed et. al., which found that germ-free mice had 42% less total body fat than their normal counterparts, even though they consumed 29% more food. Furthermore, the study revealed that by transferring microbes from normal mice into germ-free mice, the germ-free mice would record significant weight gain even though food consumption remained constant throughout the whole experiment. These findings suggested that the presence of gut microbiota significantly increases the energy harvested from the diet and promotes fat build up. These results were later echoed in other studies though more research is needed to translate these important findings in animal models to human subjects. This is a perfect timing to redesign higher education as mentioned by our Minister of Higher Education, Dato' Seri Idris Jusoh recently, in terms of producing more translational research for the benefit of our society.
It is thought that bacteria promotes weight gain by inducing the expression of our genes that regulate fat and carbohydrate metabolisms. The expression of these genes in normal circumstances does not cause problems. However, should the obese-type microbiota prove dominant in the gut, it would lead to more energy being absorbed from our diet thus making us "fat". This obese-type microbiota may also contribute to the development of obesity by triggering systemic inflammation, movement of food through the intestine and influencing hunger.
Gut Bacteria: Your "Internal" Weight-Loss Trainer
Treatment using probiotics (or beneficial bacteria of the gut) may offer novel treatments for a variety of diseases including obesity and diabetes. Pre-clinical evidence supporting the "anti-obesity" effects of probiotics mainly comes from studies on probiotics belonging to the genus Lactobacillus.
In a study, germ-free mice were introduced to human baby microbiota and fed daily with Lactobacillus paracasei, L. rhamnosus, or a placebo. Compared with the placebo, probiotics facilitated breakdown and storage of fats for energy decreased cholesterol levels and stimulated sugar metabolism. Meanwhile, L. curvatus in combination with L. plantarum effectively suppressed body weight gain and reduced fat tissue weight in mice fed a high-fat high-cholesterol diet for 9 weeks.
Interestingly, studies using the traditional Indian yogurt (or dahi) supplemented with probiotic strains of L. acidophilus and L. casei have shown that it could improve blood sugar levels in diabetic rats. In a more recent double-blind, randomised, placebo-controlled trial, supplementation with fermented milk containing L. gasseri for 12 weeks led to a significant reduction of waist fat in adult humans.
Variety Is Vitality
There is potential for gut microbiota to be manipulated for the treatment of obesity. Probiotics are currently being looked into as an option for supplementing the body with beneficial bacteria, which could potentially be promoters of weight loss. Probiotics are increasingly favoured in research, most notably because they are safe, have no apparent adverse effects, are in general well-tolerated and are appropriate for long-term use.
Common sources of probiotics include yogurt, kimchi, sauerkraut, miso soup, tempeh, and cultured milk drinks. These probiotic foods contain different types of bacteria which exert certain benefits unique to that particular species or strain.
Furthermore, though introducing your gut to weight loss-inducing probiotics may help, ensuring that you have a varied gut microbiota is much more important. There are more than 1,000 species of communal gut bacteria and we have only managed to study a few. Each species could play key roles for functions we do not yet know.
Regardless, Assoc Prof Dr Raja Affendi stresses, "A change in lifestyle is still the best option to manage weight. A well-balanced and healthy diet can help to ensure the body receives optimum amount of indigestible carbohydrates, or prebiotics, which good bacteria can use as food to flourish". He adds that metabolism of these foods by bacteria will also provide important vitamins and nutrients for our body. Eating well, exercising regularly and avoiding bad lifestyle habits like smoking not only helps to maintain healthy weight and balance of microbiota, but also decreases your chances of acquiring gut related diseases and improve quality of health and life, in general.