James Johnson. Photo credit: Martin Dee
A serendipitous discovery by a researcher at the University of British Columbia could overturn widely accepted notions about healthy eating habits.
The study, published in Cell Metabolism, examined the role of insulin, the hormone that allows the body to store blood sugar for later use as an energy source. Diabetes results from a lack of insulin.
James Johnson, an associate professor of cellular and physiological sciences, found that in animal models, too much insulin can be harmful. He gave a high-fat diet to two groups of mice: A control group of normal mice and another group bred to have half the normal amount of insulin. The control group, as expected, became fat. But the low-insulin mice were protected from weight gain because their fat cells burned more energy and stored less. The lean mice also had less inflammation and healthier livers.
Dr. Johnson concluded that extra insulin produced in the normal mice by the high-fat diet caused their obesity, which strongly suggests that mice – and, by extension, humans – may make more insulin than they need. The findings may mean that the key to maintaining a healthy weight is to continually return insulin levels to a healthy baseline by extending the gaps between meals and ignoring the widespread recommendations to consume small amounts throughout the day. In other words, cut out the snacks – and make sure not to overcompensate at mealtime.
“As crucial as insulin is for storing blood sugar, it can also be too much of a good thing,” Dr. Johnson says. “If we can maintain insulin levels at a happy medium, we could reverse the epidemic of obesity that is a risk factor for so many ailments – diabetes, heart disease, and cancer.”
While existing insulin-blocking drugs could prevent weight gain, they carry serious side effects that outweigh their benefit. Further research might lead to drugs that block excess insulin production or blunt its effect on certain targeted tissues.
Dr. Johnson, a member of UBC’s Life Sciences Institute, was not intending to study obesity. He was initially exploring whether beta cells in the pancreas, which produce insulin, were stimulated to multiply by their own insulin secretion. His discovery that low-insulin mice couldn’t gain weight was unexpected – as was the finding that most of those mice, despite dramatically lower insulin levels, still didn’t develop diabetes.
Approximately one in four Canadian adults are obese, according to measured height and weight data from 2007-2009. Between 1981 and 2007-09, obesity rates roughly doubled among both males and females in most age groups.
The research received financial support from the JDRF and the Canadian Diabetes Association.