Why Some of Us Have a Slow Response to Dieting

You stopped snacking after dinner, eliminated mindless munching, and have been avoiding the white stuff, but the pounds just won't come off. Despite putting your best effort into your new diet, you can't seem to lose any weight! You are not alone, many people have the same frustrating experience with dieting, and scientists are searching for explanations.

A new study from researchers at the Washington University School of Medicine evaluated the impact of dieting on two groups of mice. One group of mice was accustomed to the Standard American Diet (aka SAD diet), while the other group was accustomed to a low-calorie plant-based diet. We’ll call this group VEGGIE mice. When fed the same restricted diet, the SAD mice lost less weight compared with the VEGGIE mice. Both groups of mice went on the same diet, but the mice used to eating a low-calorie plant-based diet lost more weight.

Many of us can relate to these diet-challenged SAD mice. Despite multiple attempts at dieting, passing on warm french bread and mac n’ cheese, we cannot seem to drop those extra pounds. Two weeks without any weight loss? Forget it! Where’s the Ben & Jerry’sⓇ?

The standard American diet is high in refined carbohydrates, simple sugars, saturated fat and low in whole fruits and vegetables. Those of us who have spent our lifetime eating a SAD diet have fewer types of bacteria in our guts. In scientific terms, our microbiota lacks diversity. This lack of bacterial diversity lowers our response to positive dietary changes. Our gut bacteria prevent us from losing weight. Blame the bacteria!

In their study, researchers noted that the SAD mice had fewer types of bacteria in their gut. They decided to see if cohousing SAD mice and VEGGIE mice would impact the response to the diet. They found that when the diversity-challenged SAD mice mingled with their VEGGIE-mice friends, their gut bacterial colonies became more diverse. Incredibly, after mingling with the VEGGIE mice, the SAD mice started to respond to the restricted diet. The bacteria from one group of mice ended up in the other group of mice, increasing the diversity of the bacteria in the SAD mice, resulting in weight loss.

A shared space led to a greater variety of gut bugs, which led to more weight loss

Does this mean we should make more vegan friends and put away our antimicrobial sanitizer to lose weight? Possibly. But, despite our continuous shedding of bacteria, the rate at which we exchange bacteria, and the effect this has on weight loss and health is not yet clear.

What we can take away from this research is that poor food choices over the long term will negatively influence the bacteria in our gut, limiting responses to positive short-term dietary changes. If you've been eating packaged food and fast food for decades, you may not see an immediate response to a new diet. But this doesn't mean you shouldn't try! We should still make improvements to our diet, making efforts to eliminate processed foods and refined carbohydrates and adding more whole fruits and vegetables to our daily menu. But, perhaps we should abandon "dieting". Instead of multiple short-term diet attempts, a better approach may be to make a few positive dietary changes that will last a lifetime.

Creating a healthy dietary pattern will result in greater gut bacterial diversity. This diversity gives us a better chance of losing weight and will lead to long-term health benefits.

References

1. Griffin NW, et al. Prior Dietary Practices and Connections to a Human Gut Microbial Metacommunity Alter Responses to Diet Interventions. Available online 29 December 2016. http://dx.doi.org/10.1016/j.chom.2016.12.006
   
2. Image by Christine Dobrowolski using images from OpenClipArt.com. CC0 1.0.