The Biological Reason Why You Don't See Immediate Results From a New Diet

A new study reveals the hidden reason why it takes a significant amount of time before your body reaps the full benefits of a new diet.

New year, new diet.

That's the program for many Americans looking to start 2017 off right and live a healthier life. However, they should not expect to see dramatic results within a couple of weeks. A new study has discovered why it takes a significant amount of time for most people to see positive changes after starting a new diet.

Published in the journal Cell Host & Microbe, the study used mice to understand how the gut microbiome responds to drastic changes in diet. The gut microbiome refers to the dense collection of organisms living in the gut. The human gut microbiome consists of yeasts, fungi and roughly 3 to 4 pounds of bacteria. More than 5,000 species of bacteria live in the gut. Some are helpful, some are harmful and many are ambiguous. Most have long names, like "methanobreviabcater smithii" or "bifidobacterium longum," and they serve a wide range of functions.

The exact actions and purpose of many bacteria are still a mystery, but projects like the National Institute of Health's Human Microbiome Project are spending massive amounts of time and money to better understand bacteria within the body and to "look for correlations between changes in the microbiome and human health." Generally speaking, the more diverse a person's microbiome, the better. Lean, healthy people have more diverse bacteria in their gut than obese, unhealthy people, and the average American gut is less diverse than that of people in other countries with healthier populations. In most cases, a diverse gut equals a healthy gut, one that's adept at keeping the body running optimally.

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Diet Scale

For the study, researchers took fecal samples from two groups of people—one that followed a calorie-restricted, plant-rich diet and one that followed a typical, unrestricted American diet. After analyzing the samples, researchers colonized groups of germ-free mice with the different human gut communities. They then proceeded to feed the mice either the diet native to their gut or the opposite one. When the mice with a typical American gut microbiome were fed a plant-rich diet, they had a weaker response than the mice with a plant-rich gut microbiome. "Although both groups of mice responded to their new diets, mice with the American diet-conditioned microbiota had a weaker response to the plant-rich diet," Science Daily wrote of the study.

The human gut is not a blank slate, nor can it be totally remodeled with a week's worth of meals. While a new diet offers hope, one must overcome the lingering effects of previous habits before his or her body can reap the full rewards.

Interestingly enough, researchers found that integrating the mice with American diet-conditioned microbiota with mice with plant-diet-conditioned microbiota resulted in a beneficial exchange of bacteria. Science Daily summarizes:

"To identify microbes that could enhance the response of the American diet-conditioned microbiota, the researchers set up a series of staged encounters between mice. Animals harboring American diet-conditioned human gut communities were sequentially co-housed with mice colonized with microbiota from different people who had consumed the plant-rich diet for long periods of time. Microbes from the plant diet-conditioned communities made their way into the American diet-conditioned microbiota, markedly improving its response to the plant diet."

"Many of these bacteria that migrated into the American diet-conditioned microbiota were initially absent in many people consuming this non-restricted diet," said study author Nicholas Griffin. "We have an increasing appreciation for how nutritional value and the effects of diets are impacted by a consumer's microbiota," says Gordon. "We hope that microbes identified using approaches such as those described in this study may one day be used as next-generation probiotics. Our microbes provide another way of underscoring how connected we humans are to one another as members of a larger community."

Learn more about how your gut ties into almost every facet of your life in the article below.

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