Gut bacteria - a new twist on weight loss

Guest Post for MyNetDiary by Donna P Feldman MS RD

Do you ever feel like you've been cutting calories and sticking faithfully to a diet, with little effect? Frustrating, right? Well, what if it's not just about calories. What if the type of bacteria in your gut affects how many calories you metabolize? Simply restricting calories might not be the answer, if you don't also change your gut bacteria.

Previous research has shown that obese people have very different gut microbe populations compared to normal weight people. But which came first - the diet or the bacteria? Did the gut microbes cause obesity? Or did the diet encourage certain types of bacteria? The likely answer is: the diet came first. Gut bacteria are totally dependent on what we eat for survival. If we eat a diet loaded with meat, fats and sugars, with little fiber, certain types of bacteria will take over and survive. If we eat a diet high in whole plant foods, like fruits, vegetables and grains, with few sugars, a very different population of bacteria will thrive.

One clue to the impact of gut microbes on metabolism is the connection between inflammation and diet. Inflammation is linked to metabolic diseases like Type 2 diabetes and obesity. And inflammation is promoted by chronic overnutrition - too many calories from fat and simple carbohydrates. Research on specific probiotic foods, like yoghurt, suggests an anti-inflammatory effect. According to a recent review published this month, intestinal bacteria, inflammation and obesity are interconnected.

Most of the research so far uses rodents. Feeding probiotic foods like yogurt, or high fiber prebiotic foods, can change fat metabolism and suppress inflammation. A study of overweight human subjects reported this month showed that consuming specific strains of lactobacillus bacteria caused a small but significant reduction in body fat, although body weight did not change significantly during the 6 week study period. Gut bacteria did change, which may have affected intestinal fat absorption.

This line of investigation is extremely exciting and promising. But for now, we don't have enough hard facts to make specific recommendations on weight loss probiotics. There are literally thousands of choices, and the bacteria themselves can interact with each other in ways we don't understand. Probiotic capsules or probiotic-containing foods that claim to promote weight loss are premature. It's highly unlikely that you will ever be able to take a probiotic capsule and lose weight while continuing to consume a diet full of high calorie junk foods.

In the meantime, there are positive choices you can make to encourage good bacteria:

  • Eat yogurt, every day if possible. Buy yogurt with live active cultures.
  • Eat plenty of plant-based foods. Roughly 3/4 of the volume of a meal should be a variety of plant-based foods. Vegetables, fruit, nuts and grain foods like cooked grains, cereals, pasta and bread are all possibilities.
  • Minimize your consumption of processed foods, especially simple carbohydrates like sweets
  • Eat modest portions of meats. Remember, about 3/4 of your meal volume should be from plants
  • Avoid excess fats, especially animal fats and processed fats.
  • Minimize sugar intake.

Remember, calories do still count. You can't gorge on anything and expect to lose weight. The good news about the healthy-bacteria promoting foods is that they're very filling and high fiber, so it's hard to over-eat them. Just one more reason to avoid diets that are dependent on processed "diet" foods or are heavy on meat and fats. Even if weight loss promoting bacteria are identified in the future, you'll still have to eat the types of foods those microbes prefer. So far, it looks like that will be a diet heavy on plant foods.

Donna P Feldman MS RDN

is author of "Feed Your Vegetarian Teen", writes about food and nutrition at Radio Nutrition and is co-host of the Walk Talk Nutrition podcast series.

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Disclaimer: The information provided here does not constitute medical advice. If you are seeking medical advice, please visit your healthcare provider or medical professional.


Meal Planning & Diets/Healthy Eating Other Health Issues/Gastrointestinal (Gut)

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