Gut flora and losing weight

We are all unique in the way our bodies respond to food, stress, exercise and sleep. Weight loss advice is not always relevant to you. One way to get round this is by visiting a qualified nutritional expert who will discuss your history of weight gain, and identify which are the most likely causes. In addition, testing may be used to confirm if your body is likely to respond to one therapy or another.

Why are people so fat nowadays?

It is a common misconception that eating more calories and lack of exercise is the simple explanation of people being overweight. Everyone, if they reflect for long enough however, will realise that this can’t be true. We all know people who can eat exactly the same foods, and exercise at exactly the same level as ourselves and end up thinner or fatter than us. The man or woman in the street will say this is down to their metabolic rate being faster or slower, and they’ll be right.

Your lifestyle and your parents lifestyle have determined your metabolic rate. The average person in the UK is now more prone to weight gain than they were 50 years ago. There are two main reasons for this.

  • People have developed an altered set of bowel flora (trillions of bacteria that live in the bowel), that predisposes them to weight gain. This is strongly proven by studies that have found that virtually all obese people have bowel flora with certain characteristics, while slim people have a completely different looking set of bacteria. This is due in part to antibiotic overuse. 
  • Nowadays people lead a lifestyle that reinforces the weight gain by changing their bowel flora through poor dietary choices. It’s basically a powerful positive feedback loop where modern lifestyles are making it ever more difficult for people to lose weight.

So how do we change our bowel flora?

Diet, overuse of antibiotics and certain stressors are probably the key factors that determine what bacteria will thrive in our gut. Here are the steps, that will help most people to alter their bowel flora and lose weight.

Step 1: Diet

The beneficial bacteria and fungi in your intestines need the right food to prosper. In general that food consists of carbohydrate based vegetables that contain fermentable fibres. These fibres pass through the higher portions of your intestines to your colon where they feed the good bacteria.

Factors in weight loss:

  • Junk food is the key culprit in the obesity crisis we face. By “junk food”, I mean any food that is not natural. Anything in a container of any sort is suspect. If it is in a tin, carton, tetrapak or plastic container then it will likely have an ingredients list, and also be suspect. The reason for this is that food manufacturers put additives into the food to make you eat more of it, make it last longer, taste sweeter, have a better “mouth feel” etc. etc. Not all additives are harmful, but there are so many of them, many of which are harmful, that the best policy is to avoid junk food altogether. 
  • Carbohydrate and fat proportions in the diet are a key determinant of weight loss. There is a seemingly endless debate about whether “low fat” or “low carb” is better. The answer is that for most people who are overweight, low carb is a better choice. Good examples of a low carb diets are the low GI diets that you may have come across. Low GI diets work for weight loss by reducing the amount of circulating insulin in the body. Insulin is the hormone that helps us store fat (as well as carbohydrate and protein) and by limiting its levels we can make it far less likely that any foods we eat are stored as fat. 
  • Fruit and vegetable intake is key to weight control over the long term as it slowly modifies the population of bacteria and fungi in your gut. The types of vegetable and fruit are important, as the fibre they contain is the key to encouraging the healthy bacteria to thrive in your gut.

Foods for weight loss:

  • Junk food is best cut out completely. This implies that you need to cook for yourself, with ingredients that are healthier and fresher. For instance if you cook for yourself how likely are you to add in one tablespoon of monosodium glutamate, E621 or sunset yellow, E110 or BHA, E320? Not very likely, and yet these suspect additives, and hundreds of others are routinely added to most packaged foods. If cooking for yourself watch out for the sauces and other condiments that you can add as flavourings. These are very often also junk foods, and you need to inspect any labels to ensure that your sauce is a simple ingredient such as herb or spice rather than a made up mix such as one leading supermarket's red thai curry sauce, on which I counted 40 ingredients. Learning to read supermarket labels is one skill I recommend if you are not making your own sauces from scratch. 
  • Carbohydrate and fat proportions can be modified by cutting down on starchy foods such as bread, rice, pasta, breakfast cereals and all bakery products. Naturally sweet drinks and foods also come into the carbohydrate category and raise the insulin levels that you need to reduce, to lose weight. Replace the carbohydrates you cut out with fat and protein based foods or the carbohydrates contained in the fruits and vegetables discussed below. 
  • Fruit and vegetables that help develop your beneficial bowel flora include many starches such as sweet potatoes, cold potatoes as in a potato salad, parsnips, turnips, yams, squashes, courgettes, swedes and plantains. If you are from the Caribbean then “hard foods” fit in this beneficial category of foods. 
  • Fermented food and probiotics help develop a healthy bowel flora. Sauerkraut, kefir and other fermented foods are worth adding to your diet if you can cope with the mouldy smell. Yogurts with a good mix of bacterial cultures are also highly beneficial. They are traditionally used in a number of countries and help alter our bowel flora by providing friendly species of bacteria to help repopulate our bowels. In general the greater the variety of bacteria we have in our bowels the less likely we are to put on weight.

Step 2: Antibiotics

Antibiotics have been one of the few discoveries in modern medicine that has transformed health and lifespan, allowing modern surgery to take place safely and making previously deadly diseases pretty much 100% curable. However, there has been a big downside. These medicines should only be used to save lives and prevent disability. The overuse of antibiotics (including in livestock farming), has led to most of the population of the 1st world having altered gut flora. This has been a big factor in the current obesity crisis as well as contributing to the increased prevalence of autoimmune diseases such as lupus, rheumatoid arthritis, Crohn’s, colitis and type 1 diabetes.

My advice on antibiotics is to avoid them as far as possible. Never take them for a suspected viral illness as they won’t work! Many doctors in the UK within the past year have become far more reticent to prescribe antibiotics, as the possibility of antibiotic resistance is becoming more and more likely. If you want an idea of how antibiotic resistance is likely to affect you, consider that most operations can only take place because infections can be prevented. No effective antibiotics means no more heart, kidney or bone marrow transplants. It is a chilling thought.

In terms of fat loss, antibiotics drastically reduce the variability of species of bacteria living in our bowel. This has been associated time and time again with increased levels of obesity.

Step 3: Stress

Stress is an important factor for some people in their weight loss efforts. It can directly stimulate stress hormones such as cortisol and adrenaline, which can lead to either weight gain or weight loss. Stress also affects the total number and diversity of bacteria inhabiting your guts. Experiments have found that negative stressors led to fewer strains of bacteria colonising the gut, and that this led to disease related to abnormal immune responses.


So to change your gut flora for the better and thereby lose weight:

1 - Avoid most packaged food. 

2 - Eat a low glycaemic diet. 

3 - Eat plenty of foods containing fermentable fibre. 

4 - Eat probiotic foods including fermented foods.

Guidance on how to follow the above steps should be available from a trained nutritionist.

The views expressed in this article are those of the author. All articles published on Nutritionist Resource are reviewed by our editorial team.

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Milton Keynes, Buckinghamshire, MK16
Written by Robin Dowswell, BSc MFNTP
Milton Keynes, Buckinghamshire, MK16

Robin Dowswell is a Nutritional Therapist working just outside Milton Keynes. He specialises in nutrition for health as well as sports nutrition. Check out his nutrition A-Z to find out about over 50 different foods and supplements as well as information on diets for a range of conditions.

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