Very Low Effort Muscular Activity and Diabetes Risk

Marc Hamilton, PhD
Marc Hamilton, PhD, Texas Obesity Research Center, Houston

On May 6, 2015, the American Diabetes Association hosted its first National Get Fit, Don't Sit Day as part of its Wellness Lives Here SM initiative to promote workplace wellness and healthy living, and to improve organizational well-being.

National Get Fit, Don't Sit Day encouraged people to limit their time spent sitting by getting up and moving at least every 90 minutes throughout the work day.

Interestingly, the groundbreaking research that supports the recommendation to limit sedentary behavior has been funded by the American Diabetes Association and published in our peer-reviewed journals.

When Dr. Marc T. Hamilton (Texas Obesity Research Center, Houston, TX) began his research efforts in the late 1990s, he set out to study the physiological effects of intense exercise. By happenstance, when he set up experiments to look at differences in exercise time and intensity in rats, he noticed an unexpected result. He saw that light physical activity spread throughout the whole day was more effective at improving lipid and glucose metabolism than intense exercise for a couple of hours.

The Association's flagship basic research journal Diabetes published a paper in 2007, titled Role of low energy expenditure and sitting in obesity, metabolic syndrome, type 2 diabetes, and cardiovascular disease. This perspective piece, authored by Dr. Hamilton and colleagues, has been cited nearly 900 times since it was first published eight years ago and is considered a paradigm shift in recognizing inactivity physiology as distinct from exercise physiology. That is to say, that light physical activity may not feel like it takes much effort. However, at the cellular level, it activates certain health benefits that are totally separate and distinct from those resulting from periods of intense exercise. Interestingly, his research has shown that the strongest clue for how this works is through understanding that the specialized type of muscle cells activated during light activity are the ones most richly endowed with the key proteins for metabolism of fat, cholesterol, and blood sugar. This important finding provides crucial information for shaping health guidelines, especially for people who may not be able to endure intense exercise.

Since this surprising discovery and his 2007 publication, the field of inactivity physiology has mushroomed. More than 1,000 papers were published in this field in just the last few years. Many epidemiological studies have since shown correlations between inactivity and poorer metabolic health outcomes.

Still, more work needs to be done to understand the underlying effects of inactivity and light activity in humans. Over the years, Dr. Hamilton found it difficult to secure funding to pursue his research aimed at dissecting the unique set of biochemical processes in the body that respond to relatively light muscle activity. But starting this year with a grant funded by the American Diabetes Association, Dr. Hamilton is studying how interrupting sitting time with light physical activity impacts glucose and fat metabolism in the muscles of people at high risk for diabetes who do not exercise.

This effort is critical. An estimated 90 percent of the U.S. population does not exercise, and many factors beyond willpower are at play. Many of the people who have the highest risk of developing diabetes, including those who are elderly, obese or have pre-existing conditions, may not be able to tolerate intense exercise routines. Beyond that, a substantial segment of the population is employed at sedentary positions and subject to time restrictions limiting the capacity to exercise. But, this American Diabetes Association study will show whether the immediate benefits of light activity will yield improvements in insulin and lipid responses. The results of the study, and their translation to the public through awareness campaigns like the Get Fit, Don't Sit Day, have a great potential to improve health and reduce risk for diabetes.

  • Last Reviewed: November 2, 2015
  • Last Edited: November 3, 2015