
With 2016 just around the corner, it's time for the next big topic in fitness. To most people’s surprise, this may well be the gut!
Although it sounds like an unusual candidate and may not be as eye-catching as some new “cure all” supplement or awesome workout routine, it is based on a lot of research and mechanisms supporting its importance.
Shortly after birth, over 1000 species of bacteria colonise in the gut. As we age, our gut health can be affected and compromised by a host of factors, including the use of antibiotics, illness, stress, aging, bad dietary habits, toxins, and lifestyle.1
The integrity of our gut is often overlooked and its importance unknown to most individuals. However, it plays a key role in allergies, inflammatory disease, body composition (fat gain/loss), digestion, nutrient absorption, and serious diseases such as obesity, diabetes and certain cancers.2

Initial research on mice and rats highlighted the potential link of gut health to obesity and disease risk. One study in the National Academy of Science gave healthy, germ free mice a “Bacteria transplant” with unhealthy gut bacteria. They found the healthy mice increased body fat by an astonishing 57%, their triglyceride levels (fat within the blood, linked with diseases such as high cholesterol and heart disease) multiplied by 2 – 3 times the baseline amount, and insulin resistance dramatically increased.
What is more, this all occurred in only 2 weeks and with no change to their diet or lifestyle. To clarify that last sentence in case its significance is not obvious, a simple change in gut bacteria caused drastic weight gain and increased markers of disease!
A follow up study by the same author then compared a high carbohydrate and high fat diet in mice with healthy and unhealthy gut bacteria. The healthy mice gained significantly less weight; fat mass and markers of metabolic disease such as glucose (Carbohydrate) tolerance and insulin resistance were affected to a lesser degree than the mice with the bad bacteria.
Similar to the first study, this all occurred with dieting being the same between groups! The researchers highlighted several mechanisms and found that those with bad gut bacteria harvested energy into fat storage more efficiently than those with a healthy gut, which is bad news for your health and physique!
In contrast to the alteration following bad bacteria, one study provided obese mice with healthy gut bacteria. Following the feeding of a specific probiotic (healthy bacteria), L. rhamnosus PL60 caused a noticeable reduction in body fat and weight. Again, this was achieved without alteration to diet or energy balance.
If these findings transferred to humans, it could explain drastic differences in people’s ability to maintain weight or gain weight and also demonstrate the vital role of gut health on body composition, obesity and disease.
However, it is important to note that fat loss is still largely dependent on factors such as energy balance and exercise, but nonetheless the gut is clearly playing an underpinning role which can affect these variables or the overall outcome.
Although animal models are great for eliminating many variables in research, sometimes findings in mice do not cross over to humans. For obvious reasons, it is deemed unethical to give humans bad bacteria to make them ill and obese; however recent research has highlighted the importance of gut health in human models.

IBD describes chronic inflammation of part or the whole digestive tract and is common among western, economically developed countries. Research suggests it is largely caused by alterations in the gut bacteria and can lead to other serious diseases such as Crohn’s disease, arthritis and ulcerative colitis.4
Further human research has highlighted gut health as an important factor in obesity and its related metabolic diseases. Several specific types of bacteria have been shown to play a key role, for instance, the ratio of Firmicutes to Bacteroides is correlated with bodyweight and obese individuals have been found to have a high ratio.5
Other research has found a poor gut health can cause a state of chronic inflammation, which may be linked with weight gain, obesity and disease.6 Other negative alterations in gut health such as Clostridium difficile disease can not only cause the apparent health issues, but are associated with obesity. Intervention based research is now investigating the beneficial role of pre and probiotics (which improve the healthy bacteria) in obesity and disease.7,8
As mentioned, gut bacteria is affected within minutes or even before we are born! Studies in newborn babies found that the intestinal microbial colonization (bacterial formation) is altered by early feeding (natural vs artificial), birth weight, and even the delivery method of the actual birth.9
Gut bacteria has also been shown to affect our tolerance of blood glucose (Carbohydrates), which affects an individual’s body composition, health and susceptibility to disease.10
Research into diabetes has found that changes in gut bacteria may have positive effects in both type one and type two diabetes.9 Clostridium, an important strain of bacteria, has been found to correlate with glucose levels in diabetes.9
Other bacterial strains have been linked with the key mechanisms behind diabetes. Some of them have been found to specifically improve glucose tolerance and improve insulin sensitivity, both of which are vital in fat loss, muscle growth, health and disease prevention!10, 11
An unhealthy gut can also lead to gastrointestinal cancer and prostate cancer, with research showing a distinct difference in the gut bacteria for a healthy person compared to an individual with cancer.3
Interestingly, dietary admission of a specific strain of bacteria (Bifidobacterium Longum) managed to significantly suppress the incidence of colonic tumors and the degree of these tumors. Researchers suggested that this strain of bacteria may elicit a strong antitumor effect.

The benefits continue, with research suggesting that gut health has a direct correlation on our chances of developing CVD. There are several mechanisms in which this may occur, one of which is the formation of trimethylamine from gut bacteria, which may have an anti-atherogenic effect and reduce the build-up of plaque within the arteries.
Cardiovascular dysfunction may also lead to damage within the intestinal barrier, which furthers the body’s inflammatory response.12 Certain strains of bacteria such as Escherichia coli, Klebsiella pneumonia, and Streptococcus viridians may increase the gut’s permeability or resistance, which is good.
In contrast, certain other forms of bacteria may have the opposite effect on the gut’s permeability. This may lead to increased bacteria and endotoxin translocation, Krack et al. (2005) suggested that this may be an important stimulus for inflammatory cytokine to be activated in chronic heart failure.
High cholesterol is a common and well known risk factor in CVD. Three specific strains of Lactobacillus plantarum may help with cholesterol, one study by Lam et al. also found they reduce heart attack and improve ischemic (brain) function and recovery of heart attack patients.13
Although we are still in the infancy of research into the gut, it is likely that gut health can also affect:

Here are several techniques you can immediately implement to start improving your gut and reduce the bad bacteria!
Current research is only just beginning to discover all the potential and crucial roles of gut bacteria. For example, new research has highlighted that the effect of the gut on obesity may be mediated via the regulation of the microbiota-brain-gut axis and its metabolites.
Although detailed discussion of this is beyond the scope of the current article, this means our bacteria affect every aspect of our body, including the brain! This further highlights the integrated yet complex role the gut has on health, obesity and disease.
Despite it often being ignored or overlooked, your gut should be a key focus if you are interested in your body composition and health. Apply some of the simple strategies above and see how your body composition, mood, energy and overall health improve!