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March 25, 2014
Overeating and Inactivity Bring Negative Physiological AND Genetic Changes
Health is so often a simple matter of diet and exercise: a “mantra” on this blog. Now, there’s another reason to believe.
This particular study – conducted by scientists at the University of Bath, England – concerned “energy surplus,” the technical term for consuming more calories than we burn. We already know what happens when an energy surplus continues unchecked: among other poor health outcomes like obesity, it contributes to insulin resistance, the first step toward diabetes.
In particular, the team at Bath wanted to determine if exercise had effects beyond simply reducing the energy surplus by burning calories. How would they establish a methodology to find out?
The researchers corralled 26 health young men. None of them were obese, and they all exercised regularly. During baseline health assessments – which included biopsies of their fat tissue – they all showed normal metabolisms and blood sugar control. None showed any symptoms of early diabetes.
Eat a Lot More, Move a Lot Less
These healthy men were randomly assigned to one of two groups. The first ran briskly on a treadmill for 45 minutes every day; the second didn’t exercise. To more accurately assess the effects of the treadmill exercise, the men in both groups were told to otherwise reduce their movements every day, limiting their steps -- tracked by pedometers -- to about 4,000 paces.
In addition, both groups were instructed to substantially overeat, increasing everyone’s energy surplus.
If both groups were eating the same amount of food, the treadmill group would show lower energy surpluses than the stationary group. But the scientists wanted to measure biological differences between the two groups if ONE exercised while BOTH maintained similar energy surpluses.
So, study leaders fed the exercising group more than the inactive group – adding to their diets the calories equivalent to what they had burned on the treadmill.
After only seven days on their regimens, the men returned to the lab. Among other tests, study leaders took insulin measurements and checked the men’s fat cells again. The inactive men showed a significant, unhealthy decline in their blood sugar control – a surprisingly quick step forward on the road to diabetes.
Physiological AND Genetic Changes
Those inactive men showed something perhaps more worrying. Sophisticated genetic testing techniques showed that their fat cells were overexpressing genes that could contribute to bad metabolic changes, and underexpressing other genes linked with healthful metabolic maintenance.
The treadmill subjects – even though their energy surpluses roughly matched those in the sedentary group – showed no such negative changes. Their blood sugar controls remained strong. Their fat cells showed fewer potentially negative alterations in gene expression than their inactive counterparts.
Dr. Dylan Thompson, study author and professor of health sciences at the University of Bath, said, “Exercise seemed to completely cancel out many of the changes induced by overfeeding and reduced activity.” And if exercise didn’t fully offset the effects of overeating and otherwise reduced activity, it reduced the negative impacts.
The study suggests that metabolic effects of overeating and inactivity – the two contributors to energy surplus – are perhaps more multi-faceted than we might have thought: the energy surplus in the sedentary group sparked not only the physiological changes we might expect, but also genetic ones.
Just HOW exercise mitigated those negative results, especially the genetic ones – is a question this study doesn’t address. There are other problems, too. The testing interval was brief (though results were surprisingly dramatic), and it tested only fit, young men. Would results be similar for women and seniors?
Nonetheless, these findings offer another encouragement – now that spring is here (officially, anyway) -- to put on the walking shoes, the hat, and the sunblock . . . and get moving.
Here’s the study's abstract from PubMed.gov.