Eating more than usual for a week may not be bad, as long as people exercise regularly, too.
Is this disastrous for health? Apparently not, as long as people keep exercising. These are the findings of research presented at the American Physiological Society (APS) Integrative Biology of Exercise VII meeting in Phoenix, AZ.
Obesity affects 36.5 percent of Americans, and it is a public health issue of major concern.
It is often associated with type 2 diabetes and other "lifestyle" diseases, especially cardiovascular disease, that come under the umbrella of metabolic syndrome.
Metabolic syndrome involves a cluster of cardiometabolic risk factors. These include a large waist circumference, high levels of triglycerides and blood glucose, and hypertension, or high blood pressure. It also features low levels of high-density lipoprotein (HDL), or "good" cholesterol.
A lack of exercise and an unhealthy diet have been linked to obesity and metabolic syndrome.
Previous studies have concluded that increasing aerobic fitness may reverse the early symptoms of metabolic syndrome.
Even occasional bingeing can cause damage
Even people who overeat only from time to time may experience an increase in adipose tissue and metabolic abnormalities. There is evidence that just a week of overeating can have a negative effect on glycemic control and insulin sensitivity, putting people at risk of prediabetes.
Other evidence suggests that exercise can protect against the metabolic damage that results from overeating.
However, exactly what impact exercise has on the structure and function of fat tissue remains unclear.
Researchers from the University of Michigan in Ann Arbor, wanted to know what would happen to people's fatty tissue if they continue to exercise during a week-long blowout.
The team carried out a pilot study involving four lean and active adults, aged between 21-26 years.
They hypothesized that regular aerobic exercise during a week of overeating would protect metabolic health, preserve lipolytic response - the breakdown of lipids - and prevent inflammation of the fatty tissue.
The participants consumed 30 percent more calories in one week than they usually did. They continued to exercise as usual. This included at least 2 ½ hours of aerobic exercise spread over at least 6 days of the week.
The study authors, led by Alison C. Ludzki, measured oral glucose tolerance levels and samples of abdominal fat prior to the week of overeating, and again at the end.
To measure for inflammation, they looked at markers of inflammation in fat tissue - such as pJNK/JNK, pERK/ERK - or circulating C-reactive protein
Exercise appears to reduce hazards of overeating
In people who do not exercise, the markers of inflammation in fat tissue would normally increase after a week of overeating, but this time the results were different.
Instead, the active participants in this study showed no signs of inflammation in their fatty tissue, and no change in glucose tolerance or the chemical breakdown of fat.
The researchers conclude:
"Our preliminary findings expand on existing work to support a protective role of exercise in the metabolic response of adipose tissue to brief periods of overeating."