When faced with a loaded table amid a feasting crowd and festive atmosphere, it’s hard not to loosen your belt and indulge.

But there hasn’t been much research into the effects of occasional overeating on the body’s blood-sugar control system, weight gain, or body composition.

Chronic overeating leads to weight gain and chronically high blood sugar levels, which both promote the type 2 diabetes that afflicts some 28 million Americans.

The blood-sugar control system centers around release of insulin in response to foods, and the ability of our cells to absorb blood sugar in response to that key metabolic hormone.

The question is whether occasional over-indulgence raises your risk for weight gain, diabetes, or both.

Preliminary research from Australia suggests that periodic feasting doesn’t disrupt the body’s blood-sugar control system — but it did yield a cautionary finding about belly fat.

Aussie scientists examined the effects of overeating
The new findings come from the Institute for Physical Activity and Nutrition at Australia’s Deakin University.

The Aussie team set out to study the impacts of adding sweet, fatty, high-calorie fare to an otherwise balanced diet for a few days versus four weeks (Morrison DJ et al, 2019).

The participants in this two-phase study were eight healthy, normal-weight young men, whose average age was 22 years.

The subjects’ weight, total body fat, abdominal fat, blood sugar levels, and insulin levels were measured before and after each period of overeating.

Five days of overeating: Study phase 1
The volunteers engaged in five days of overeating during which they consumed about 1,000 extra calories from of snacks and sweets, including chocolates and potato chips.

The foods providing the excess calories were added to a typical Australian (and American) non-holiday diet comprised of about 55% carbohydrates, 35% fat, and 15% protein.

Following five-days of overeating, the researchers were surprised to see no changes in fasting blood sugar levels or the amino acid C-peptide, which is released when the body pumps out insulin.

And the five days of calorie-bingeing did not significantly increase the men’s total body fat or weight.

However, the five-day binge raised the amount of abdominal fat surrounding internal organs — called visceral fat — by about 15%.

That substantial increase in visceral fat is cause for concern, because excessive amounts are linked to inflammation, insulin resistance, type 2 diabetes, high blood triglycerides (fats), and cardiovascular disease.

28 days of overeating: Study phase 2
Like the five days of overeating, 28-days of overeating did not raise the men’s total body fat, fasting blood sugar levels, or insulin levels.

And, somewhat surprisingly, 28 days of overeating did not add more visceral fat beyond the 15% increase caused by the five-day binge.

What’s the take-away?
First, it’s important to stress that this was a small study that involved young, healthy men.

The results suggest that the body’s blood sugar control system adapts to temporary, excessive calorie intakes. The Australian team proposed that this might be because the volunteers' basically healthy main meals may have blunted the effects of the sweet, fatty extra calories.

And just five days of overeating caused the men to accumulate extra visceral fat, which — as we noted above — exerts negative metabolic effects that raise the risk for chronic diseases.

Whether the health, youth, and gender of the volunteers protected them from greater negative effects isn’t clear, but seems plausible.

It’s unfortunate that the volunteers weren’t followed for longer, to see whether, how quickly, and by how much the extra visceral fat might have shrunk after they returned to a normal diet.

Overall, the Aussie team's findings suggest that if you consume excess calories a few times a year, you’ll may do yourself relatively little harm, but may add some worrying belly fat.

But they certainly suggest that it’s smart to stick to the healthiest most nutrient-dense feasting fare possible: vegetables, fruits, seafood, leaner meats, nuts, and legumes like beans and lentils.

These kinds of whole, lower-carb foods — prepared with low-calorie, antioxidant-rich seasonings like herbs and spices — will seriously satisfy your palate and appetite without excess calories!


  • AHA/International Atherosclerosis Society Joint Session. Visceral Adiposity and Cardiovascular Disease. Accessed at https://aha.ondemand.org/aha/sessions/467/view
  • American Physiological Society. It’s OK to Indulge Once in a While: The Body Adapts to Occasional Short-term Overeating, Study Says. Accessed at https://www.the-aps.org/detail/news/2019/04/25/body-adapts-occasional-short-term-overeating?SSO=Y
  • Centers for Disease Control & Prevention (CDC.) Type 2 Diabetes. Accessed at https://www.cdc.gov/diabetes/basics/type2.html
  • Endocrine Society/ Endocrine News. Dangers of Visceral Fat. https://endocrinenews.endocrine.org/the-dangers-of-visceral-fat/
  • Morrison DJ, Kowalski GM, Bruce CR, Wadley GD. Modest changes to glycemic regulation are sufficient to maintain glucose fluxes in healthy young men following overfeeding with a habitual macronutrient composition. Am J Physiol Endocrinol Metab. 2019 Jun 1;316(6):E1061-E1070. doi: 10.1152/ajpendo.00500.2018. Epub 2019 Apr 9. Accessed at https://www.physiology.org/doi/full/10.1152/ajpendo.00500.2018