Fasting and eating smaller and earlier dinners has many health benefits
It has long been known that what and how much you eat can influence your weight and risk of chronic illness. Now researchers are focusing on the effects of when you eat.
Studies suggest that intermittent fasting—typically, eating only during an 8-hour period or eating only every other day—could have many potential benefits, including improvements in glucose (blood sugar) and cholesterol levels, blood pressure, and weight. Done in a healthful way, intermittent fasting holds promise for controlling inflammation and lowering the risk of type 2 diabetes, heart disease, and even some cancers.
The benefits are thought to result from a process called metabolic switching, which is when the body goes into a fasting state and begins using body fat instead of glucose to meet its energy needs.
Intermittent fasting helps preserve the body’s normal interplay between the hormone insulin and blood glucose, preventing insulin resistance (when the body doesn’t respond properly to it). Metabolic switching also signals the body to activate maintenance and repair systems, which aid in disease prevention.
But intermittent fasting isn’t for everyone. “Going for long periods without food may be too extreme for some older adults, people with diabetes, and those who must take certain medications at designated hours, among others,” says Dorothy Sears, PhD, a professor of nutrition at Arizona State University College of Health Solutions in Phoenix.
Dial back your dinner hour
Research suggests that it’s best to finish eating between 6 p.m. and 8 p.m. As bedtime approaches, melatonin increases and insulin output begins to drop. That means blood sugar climbs higher and circulates for longer because there isn’t enough insulin to clear it quickly. Research has linked late-evening eating to a greater risk of obesity, type 2 diabetes, and heart disease. In a recent study by Johns Hopkins University, for example, healthy people who ate dinner at 10 p.m. saw greater spikes in blood sugar, slower body-fat breakdown, and increases in cortisol, a hormone thought to be involved in weight gain, compared with a group who ate the same meal at 6 p.m.
Slim down your supper
Most Americans consume almost 45 percent of their total daily calories at dinner and in an after-dinner snack. A healthier goal, Sears says, is 30 percent. That’s 600 calories for someone who usually eats 2,000 calories a day. For example, in 2013, Israeli researchers looked at the effects of eating a small dinner and a large breakfast vs. a large dinner and a small breakfast in a study involving 93 overweight women. Both groups ate the same lunch and the same overall number of calories. After 12 weeks, those who ate the lighter dinners lost more weight, had a smaller waist, and had better metabolic profiles than the women in the other group.
One way to downsize the dinners that you prepare is to make them the healthiest meal of the day. Try eating lots of vegetables, which are naturally low in calories, suggests Courtney M. Peterson, PhD, an assistant professor in the department of nutrition sciences at the University of Alabama at Birmingham. That means you can eat a large portion so that you’re not hungry afterward and still consume fewer than 600 calories. The fiber from those foods will also help you feel fuller.
And if you don’t overdo it on calories in the evening, Peterson says, you can afford to have a bigger breakfast and lunch, when your body is primed for food processing.
Phase out bedtime snacks
For all the reasons mentioned here, “our general rule is ‘no food after dinner,’” says Krista Varady, PhD, a professor of nutrition at the University of Illinois at Chicago. It’s probably the most important change you can make. “I think the lack of nighttime snacking is the main reason we see such great decreases in insulin resistance in time-restricted eating studies,” she says.
If you must eat a snack, have a small portion of a food low on the glycemic index (GI)—a measure of how quickly a food raises blood glucose—such as celery, cucumbers, apples, blueberries, or raspberries. Many typical snacks—cookies, chips, crackers—are high GI, and “research suggests that it is metabolically unhealthy to eat foods with a high glycemic index late in the day,” Peterson says.