Healthy Food & Healthy Living by Dr. Ayala

Does the microbiome affect diabetes risk?

Type 2 diabetes is a global epidemic and one of the most common conditions impacting people's health. The incidence of this chronic disease and its many consequences is rising, as type 2 diabetes now presents at younger and younger ages. It is estimated that as many as 9.3 percent of the world population had diabetes in 2019, and that by 2030 the rates will surpass 10 percent.

The risk of developing type 2 diabetes is clearly related to obesity and to genetic predisposition. Diet is also a major contributor, but not by the simplistic way people may imagine: People with no sweet tooth at all can also be at increased risk of type 2 diabetes due to poor diets; it’s not just about eating sweets and added sugars. Diabetes is an impairment of sugar metabolism, leading to too much sugar in the bloodstream instead of our cells. Diet and exercise habits affect our body’s sugar metabolism in profound ways, and the fiber and fat that you eat, and how much you move, change how your body deals with glucose, the body’s main fuel, regardless of how much candy and soda you ingest.

Partners in sugar metabolism

But it’s not just the cell's metabolic machinery, pancreatic hormones and the liver that take part in metabolizing our sugars.

Each of us is home to a whole universe of microorganisms: trillions of bacteria, fungi and viruses. Microbial life outnumbers our own cells 9 to 1, and its genetic material outweighs our own 150 to 1. Our inhabitants, our microbiome, we’re finding out, play a role in our immune system, our endocrine system, our propensity for weight gain, our risk of several diseases, our energy levels, our mental state and our mood.  

Do the microbes living in our gut affect how our body deals with sugars and our susceptibility to type 2 diabetes?

A new study in the American Journal of Clinical Nutrition looks at the evidence connecting gut microbes to insulin resistance and glucose intolerance. The researchers identified 45 relevant studies tying specific gut bacteria to sugar metabolism. 

The researchers found that several types, 6 especially, were linked with sugar and insulin metabolism. Some of these bacteria are protective and their presence is associated with lower risk, yet the presence of other bacteria is inversely correlated with diabetes risk. These links seem to be independent of weight status and of diabetes drugs.

One of the mechanisms in which gut bacteria affect health outcomes may be their production of short chain fatty acids. Short chain fatty acids are produced by bacteria when they break down and ferment dietary fiber and resistant starch. 

And indeed, the presence of short chain fatty acids and other metabolites produced by gut bacteria seems to correlate with sugar control, suggesting that short chain fatty acids may be mediating the microbiome’s effect.

Our microbiome probably plays a role in the development of diabetes. But we also, in turn, affect our microbiome to a great extent. A study in Nature finds that just 2 percent of our gut microbiome profile is genetically determined, and the rest is affected by the environment and by lifestyle.

Helping your helpers

The gut microbial community is dynamic, and depends on many factors, including age, medications, genes, exercise,  and especially diet.

Boosting a healthy microbiome doesn’t require any probiotics, nor are any lab tests, supplements or special foods needed. To improve the gut population it’s recommended you eat whole plant foods (including many types of fruit, veggies, legumes, beans, grains etc.,) lots of fiber, embrace variety in your diet, and reduce refined and highly processed foods.

Dr. Ayala

Exercise for the diet resistant

Exercise is a fundamental and super important key to wellness. Physical activity helps prevent diseases, it slows aging, and boosts mental function. It makes you look and feel better. 

But despite what junk and fast food manufacturers suggest in their clever marketing, tying sugary drinks to athletes and the olympic games, exercise will not enable you to burn off all that many extra calories, and on its own – without a reduction on caloric intake – exercise yields less than expected weight loss. 

An exercise deficit issue?

We can’t really outrun the fork and out-exercise a poor diet. 

Obesity isn’t an exercise deficit problem, it’s mostly an overeating and poor diet problem, Americans aren’t that much less active than they were a few decades ago, and exercise alone isn’t a weight loss plan, studies have shown. The calories burnt by exercise are at least partly compensated for, through energy conservation during the rest of the day and by a vigorous appetite and post-workout eating.

Most overweight people who try to lose weight don’t respond to exercise alone that much, but that doesn’t mean that exercise doesn’t help you lose weight. Exercise not only helps burn calories and keep muscle mass during weight loss, it also helps with improving your diet, as people who pursue fitness often find it easier to eat better – exercise often starts and perpetuates a virtuous wellness cycle. 

And now, a new study in eBiomedicine, part of the Lancet, finds that exercise may play a pivotal role in weight loss for a subset of people. For these people, exercise isn’t just a few more “calories out” in the energy balance sheet – exercise actually changes their metabolism.

Most people lose weight when they reduce their caloric intake, but a subset of people lose much less than expected despite adhering to diet programs. The researchers looked at the clinical records of 5000 women, and identified the 20 percentile who were most and least sensitive to diet, based on their weight loss on a 6-week 900 calorie/day supervised diet. They then studied 10 diet-resistant and 10 diet-sensitive obese women among them. These 20 women were put on a closely supervised exercise regimen. Exercise included weight lifting and treadmills, and was done 3 times a week for 6 weeks. The women were followed by weight and body composition measurements, as well as blood and muscle function tests, and muscle composition studies, using a muscle biopsy.

Flawed one size fits all 

The exercise training had minimal effect on the diet-sensitive women, but among the diet resistant women it changed body composition and muscle metabolism – it increased the mitochondrial content and metabolism in their muscle – and enhanced fat loss.

Besides offering hope for the people who find weight loss especially challenging, this study emphasizes that a personalized approach to obesity is warranted. “In cases in which diet-adherent individuals fail to achieve successful weight loss through caloric restriction, exercise may preferentially enhance their weight loss capacity by reprogramming skeletal muscle metabolism to enhance oxidative processes, consistent with our findings in biopsied muscle and derived primary muscle cells,” the authors write. 

Exercise is recommended for every human out there, for fitness’ sake, and definitely for people trying to lose weight. It may play an especially crucial role for a subset of us, whose positive and weight-altering reaction to exercise is uniquely greater, and in which physical activity over-performs.

Dr. Ayala