Recent studies have demonstrated that the makeup of your intestinal flora (bacteria in your gut and intestines) can have an impact on your weight, and your ability to gain or lose weight.
Research also suggests that as much as 20 percent of the weight loss achieved from gastric bypass, a popular weight loss surgery, is actually due to shifts in the balance of bacteria in your digestive tract.
To investigate the potential link between gastric bypass surgery and changes in gut flora, fattened-up mice were divided into two groups. The test group underwent gastric bypass surgery while the control group received sham surgery. After the sham surgery, the controls were further divided into two groups: One received a fatty diet; the other a weight-loss diet.
In the group who received the bypass surgery the microbial populations quickly changed following surgery, and the mice lost weight. In the control group, the gut flora didn’t change much, regardless of their diet.
Previous research has also shown that lean people tend to have higher amounts of various healthy bacteria compared to obese people. For example, one 2011 study found that daily intake of a specific form of lactic acid bacteria could help prevent obesity and reduce low-level inflammation.
In this study, rats given the bacterium while in utero through adulthood put on significantly less weight than the control group, even though both groups of rats ate a similar high-calorie diet. They also had lower levels of minor inflammation, which has been associated with obesity.
Similarly, gut bacteria have also been shown to impact weight in human babies. One study found babies with high numbers of bifidobacteria and low numbers of Staphylococcus aureus — appeared to be protected from excess weight gain.
This may be one reason why breast-fed babies have a lower risk of obesity, as bifidobacteria flourish in the gut of breast-fed babies. Probiotics also appear beneficial in helping women lose weight after childbirth when taken from the first trimester through breastfeeding.
Two other studies found that obese individuals had about 20 percent more of a family of bacteria known as firmicutes, and almost 90 percent less of a bacteria called bacteroidetes than lean people. Firmicutes help your body to extract calories from complex sugars and deposit those calories in fat. When these microbes were transplanted into normal-weight mice, those mice started to gain twice as much fat. This is one explanation for how the microflora in your gut may affect your weight.
Another study from 2010 showed that obese people were able to reduce their abdominal fat by nearly five percent, and their subcutaneous fat by over three percent, just by drinking a probiotic-rich fermented milk beverage for 12 weeks. Given that the control group experienced no significant fat reductions at all during the study period, this is one more reason to consider probiotics.
Probiotics have also been found to benefit metabolic syndrome, which often accompanies obesity. This makes sense since both are caused by a diet high in sugars, which leads to insulin resistance, fuels the growth of unhealthy bacteria, and packs on excess weight.
Dominick Walsh is a blogger for Performance Nutrition and TMRzoo.com and covers all men’s health topics and exercise issues including protein powders, diets, weight loss, weight lifting supplements, fat burners and supplement reviews. Dominick’s columns cover everything you need to know about your pre, during and post workout nutrition.