To highlight this, research during the past 10 years has shown that probiotics play an important role in weight gain and influence the obesity epidemic we are now facing. If you do not consider a program of probiotics, any weight loss program is doomed to fail. The probiotics in our gut can influence both our hunger and food cravings, primarily through our genes. A breakthrough paper published in Nature in December 2006 reported that microbial populations in the gut are different between obese and lean people, and that when obese people lost weight, their microflora reverted back to that observed in a lean person, suggesting that obesity may have a microbial component. Since then, a lot of research has linked healthy probiotics with healthy weight and weight loss - primarily through epigenetic control and changing how the genes are expressed.
We now know that out-of-balance bacteria damage the gut and diminish digestion and absorption and cause weight gain - as well as bloating, gas, fatigue, constipation, diarrhoea, rash, eczema (which are also often symptoms of excess weight) and much more. Digestion and nutrient absorption need healthy gut ecology with lots of gut-friendly bacteria. These bacteria assist the immune system. They help with digesting food so that we can absorb all the nutrients - manufacturing vitamin K and the B group vitamins that protect us from toxins - as well as communicate with our genes to tell us to feel full and increase our metabolism.
A study with 50 pregnant women revealed that women who experienced excessive weight gain during pregnancy had more Escherichia coli (E. coli) bacteria in their guts, and fewer bifidobacteria than women with normal weight gain during pregnancy. This demonstrated that gut microbiota composition is related to body weight, weight gain and metabolic biomarkers during pregnancy (1). The study builds on earlier studies that linked gut microflora and obesity.
Antibiotics and babies
Similarly, studies looking at long courses of taking antibiotics show they put babies and toddlers at higher risk of obesity when they grow up. The research shows low doses of penicillin early in life can alter natural populations of gut microbes, which in turn may affect metabolism and lead to higher rates of obesity later in life (1). Studies have found that children who had antibiotics before six months of age were more likely to be overweight as seven-year-olds.
Animal studies point to a window in early life when changes to the microbiome appeared to have a serious impact on metabolism and weight gain. In mice, the window was the first month of life. If a similar vulnerable period exists in humans, it is likely to be the first six months. Hence the importance of breast milk in this period, which is rich in prebiotics to feed the health gut.
The problem arose when antibiotics wiped out some types of gut bacteria but allowed hardier ones to thrive. This change in composition of the microbiome had a long-term impact on metabolism that persisted even when the population of gut microbes had returned to normal several weeks later. Four weeks of antibiotics was enough to perturb the microbiome, and even though it returned to normal after a few weeks, the mice still became fat. Mice that had been given antibiotics during the first month of life were 25% heavier and had 60% more fat than controls. Disrupting the microbiome seemed to exacerbate the effects of a high-fat diet, too, with animals on antibiotics gaining more weight than others who were not given the drugs. For unknown reasons, males put on more weight than females.
To control for the effects of genetics, one study found four pairs of human twins, with one twin obese and the other lean. Researchers collected the stools of each twin, then transferred the twins' bacteria to sets of mice (3). Fed an identical diet, the mice with bacteria from an obese twin became obese, whereas mice with bacteria from a thin twin remained lean. The researchers then tested what would happen when mice with different bacteria were housed together (mouse droppings help to transfer bacteria). Bacteria from the lean mice made their way to the mice with the obese twin's bacteria, preventing those mice from gaining weight and developing other metabolic abnormalities. But the phenomenon did not work in reverse.
Gut bacteria can improve our weight control through a number of mechanisms including communicating with our genes, and controlling our eating behaviours and cravings. They do this through changes in gene expression and the cellular reactions in the human intestine. In one study, after supplementation with probiotic bacteria (Lactobacillus) changes in the activity of hundreds of genes was observed (4).
Bacteria control our food choices
It seems that our eating behaviour is controlled by the bacteria within us, which can affect both our cravings and moods to get us to eat what they want, and often are driving us toward obesity. The microbes influence human eating behaviour and dietary choices to favour consumption of the particular nutrients on which they grow best, rather than simply passively living off whatever nutrients we choose to send their way. Bacterial species vary in nutrient requirements - some prefer fat and others sugar, for instance. But their vying with each other is not just for food or to retain a niche within our digestive tracts (5). Some of the potential mechanisms for microbial control overeating behaviour including microbial influence on reward and satiety pathways, production of toxins that alter mood, changes to receptors including taste receptors, and hijacking of the vagus nerve, the neural axis between the gut and the brain.
The gut bacteria may be affecting our eating decisions in part by acting through the vagus nerve, which connects 100 million nerve cells from the digestive tract to the base of the brain (2). It appears that microbes have the capacity to manipulate behaviour and mood through altering the neural signals in the vagus nerve, changing taste receptors, producing toxins to make us feel bad, and releasing chemical rewards to make us feel good. In mice, certain strains of bacteria increase anxious behaviour. In humans, one clinical trial found that drinking a probiotic containing Lactobacillus improved mood in those who were feeling the lowest.
A number of recent studies have also highlighted the influence of toxins (endotoxins) produced by the harmful gut bacteria. A randomised, double blind, placebo-controlled study was conducted, in which patients with higher BMI (>25 kg/m2) and waist circumference (>85 cm) correlations between gut microbiota and change in body composition indicate that probiotics may influence energy metabolism in obesity. Correlation between endotoxin level and weight reduction indicates that probiotics may play an important role in prevention of endotoxin production, which can lead to gut microbiota dysbiosis associated with obesity (6).
Probiotics influence weight loss
Fortunately, we can influence the compatibility of the gut microbiome by deliberately altering what we ingest, as it is evolving on the time scale of minutes. The speed with which the microbiome can change may be encouraging to those who seek to improve health by altering microbial populations. The microbiota are easily manipulatable by prebiotics, probiotics, and dietary changes. Altering our microbiota offers a novel approach to otherwise intractable problems of obesity and unhealthy eating.
Natural foods help the friendly gut bacteria stay healthy, and thus our digestion and nutrient absorption are also optimised. In a double-blind, placebo-controlled, randomised trial, over 24 weeks the mean weight loss in women in the probiotic-supplementing group was significantly higher than that in women in the placebo group after the first 12 weeks, whereas it was similar in men in the two groups. Women in the probiotic group continued to lose body weight and fat mass during the weight-maintenance period, whereas opposite changes were observed in the placebo group. The probiotic-induced weight loss in women was associated not only with significant reductions in fat mass and circulating leptin (hormones that make us feel satisfied) concentrations but also with the relative abundance of "healthy" bacteria (7).
In line with this, a study found that probiotic supplements during pregnancy reduce the risk of obesity later in a baby's life, with fewer births of larger babies (8). The scientists reported that probiotic supplements during the first trimester of pregnancy help women lose weight after the infant's birth. Supplements containing lactobacillus and bifidobacterium were associated with less central obesity. The women who got the probiotics fared best. One year after childbirth, they had the lowest levels of central obesity as well as the lowest body fat percentage (9). Another study reported that probiotics supplements to 256 women during their first trimester of pregnancy reduced the risk of gestational diabetes during pregnancy by 20% and reduces the risk of obesity later in a baby's life (8).
In another study, treatment with Bifidobacterium significantly decreased fat mass in obese (7.83 g) and diabetic mice (1.89 g). This was reflected as reduced weight gain and improved glucose tolerance as well as decreased plasma lipopolysaccharide levels (LPS), liver inflammation, and E. coli adhesion in the distal gut (10). Circulating endotoxins (LPS) has been linked to the development of mouse obesity (11,12,13). The translocated bacteria and bacterial fragments stimulated the proliferation of adipose tissue precursors and favoured body weight gain through a process associated with LPS-induced inflammation of adipose tissue macrophages (14).
Other health benefits
While improving the gut microbiome with probiotics and prebiotics is associated with weight loss and reduced weight gain, it also improves many other aspects of our health. A review of 13 randomised controlled trials representing 513 obese adult participants found prebiotic supplementation reduced plasma total cholesterol and LDL-c concentrations in overall analysis, and reduced triglycerides and increased HDL concentrations in diabetic trials. Synbiotic (probiotic and prebiotic) supplementation reduced plasma fasting insulin and triglyceride concentrations. The improvement of the evaluated parameters supports prebiotics and synbiotics supplementation as an adjuvant therapy in obesity-related comorbidities, such as dyslipidemia and insulin resistance (15).
However, before you go out and buy lot of probiotics and yoghurt products and expect miracles, understand that not all bacteria and probiotics are equal. Find a super probiotic species with human strains. Also don't expect any advantage unless you feed the probiotics the right food. Not what you crave, the sugar and fat, but what they need: plant-based foods, especially well chewed raw or put through a smoothie maker (not juice).
DISCLAIMER: Dr Peter Dingle is a researcher, educator and public health advocate. He has a PhD in the field of environmental toxicology and is not a medical doctor.
References:Sanz et al. 2010Alcock et al. 2014Gordon et al. 2013van Baarlen et al. 2010Aktipis et al. 2014Lee et al. 2014Sancheza et al. 2013Luoto et al 2010Santacruz et al. 2010Stenman et al. 2014Caniet et al. 2007aBackhedet et al. 2007; Rabotet et al. 2010Lucheet et al. 2013Bruna et al. 2014
Dr Peter Dingle (PhD) has spent the past 30 years as a researcher, educator, author and advocate for a common sense approach to health and wellbeing. He has a PhD in the field of environmental toxicology and is not a medical doctor. He is Australia’s leading motivational health speaker and has 14 books in publication.