Experts have long warned that skipping meals is an ineffective way to lose weight, as it ultimately leads to overeating and poorer food choices. But according to a new study, skipping meals affects more than just our eating behavior — it can actually set off a series of maladaptive metabolic effects that promote fat-storage around the waist and increase the risk of diabetes and heart disease.
The study, published in The Journal of Nutritional Biochemistry, found that mice that ate all of their food as a single meal and fasted the rest of the day developed insulin resistance in their livers – a telltale sign of prediabetes – and excess fat in their abdomens. When the liver becomes less sensitive to insulin, it keeps producing glucose when it is not needed, so the blood ends up with too much sugar and the excess is stored as fat. This likely explains why the mice accumulated more abdominal fat, the researchers said.
“This does support the notion that small meals throughout the day can be helpful for weight loss, though that may not be practical for many people,” said Dr. Martha Belury, professor of human nutrition at Ohio State University and senior author of the study. “But you definitely don’t want to skip meals to save calories because it sets your body up for larger fluctuations in insulin and glucose and could be setting you up for more fat gain instead of fat loss.”
For the experiment, Dr. Belury and her colleagues divided mice into two groups: the control and the intervention group. Controls were given their full daily food ration once a day, which they nibbled throughout the day. At first, the intervention group was given a restricted calorie diet. For 3 days their daily food ration had half the calories of that given to the controls. This initiated gorging behavior – they ate all their food in one session and then fasted.
Then, over another 3 days, the intervention (now gorging) mice were gradually given more and more calories until their rations were the same as the controls. But instead of going back to nibbling like the controls, they continued with their gorging and fasting pattern, eating all of their food in a period of 4 hours and then fasting for 20 hours.
By the end of the study, the weight of the intervention mice was similar to the control mice. However, intervention mice had accumulated more weight around their midsection. Weight around the midsection of mice was likened to abdominal fat in humans, which is associated with insulin resistance and higher risk for type 2 diabetes and heart disease. In women, this type of fat also increases breast cancer risk.
In addition to storing more abdominal fat, the intervention mice also had higher levels of inflammation when they gorged then fasted. This was accompanied by higher activity in genes that promote storage of fatty molecules and plumper fat cells, especially in the abdomen. The researchers attribute these changes to spikes and then severe drops in insulin caused by fasting.
When insulin levels fall — for instance, when we are asleep — the liver pumps glucose into the blood to feed the brain. When we eat, the pancreas pumps out insulin to move glucose from the blood to the cells that need it for energy. This rise in insulin instructs the liver to stop pumping glucose. When they examined the intervention mice, the researchers found that glucose was lingering in their blood — suggesting that the liver was not receiving the insulin message that tells it to stop producing glucose. Dr. Belury explains how this links to diabetes:
“Under conditions when the liver is not stimulated by insulin, increased glucose output from the liver means the liver isn’t responding to signals telling it to shut down glucose production. These mice don’t have type 2 diabetes yet, but they’re not responding to insulin anymore and that state of insulin resistance is referred to as prediabetes.”
Eating your way to weight-loss
Skipping meals also sabotages weight-loss efforts by triggering changes in our appetite hormones and in the brain regions responsible for processing food- and appetite-related cues. For example, research shows that fasting or severely restricting caloric intake can actually make unhealthy food more attractive. When people on restricted diet plans are shown pictures of unhealthy but appetizing food, their brains display hyperactivity in regions implicated in motivation and reward processes, indicating heightened responsiveness to food. Fasting and calorie deprivation also stimulate production of the appetite hormone grehlin, which leads to cravings for calorie-dense foods.
While the research is pretty clear on the pitfalls of skipping meals, there is conflicting evidence as to whether eating frequent small meals has any specific weight-loss benefits. A 2012 study published in the journal Obesity followed 50 people who were asked to exercise at least 200 minutes a week and to eat from 1,200 to 1,500 calories a day. They were divided into two groups, one eating three meals a day and the other eating six. People in both groups lost similar amounts of weight. But the group eating six smaller meals reported feeling less hungry. Additionally, cross-sectional studies reveal that people with a healthy body weight tend to eat more frequently than those who are overweight.
On the other hand, a 2011 review of the research concluded that increasing meal frequency does not have beneficial effects for weight loss, while eating larger meals less frequently could boost feelings of satiety. And a small study published in 2014 found that people with diabetes who ate just two meals a day — breakfast and lunch — lost slightly more weight than those who ate six smaller meals of the same nutritional and energy content. Two meals a day also led to a greater decrease in liver fat content and a bigger increase in insulin sensitivity than six smaller meals.
Ultimately, the best eating plan is the one that you will stick with. A good place to start is by figuring out how many calories you should be eating each day. The Mayo Clinic website has a “Calorie Calculator” to help you determine the number of calories your body needs to maintain its weight, based on your age, height and level of exercise. Then, you can plan for how to best spread those calories throughout the day.