Can changing when you eat, rather than what you eat, make it easier to lose weight? UR Medicine nutrition expert Dr. Thomas Campbell weighs in on intermittent fasting and what works over the long term.
The every-other-day diet, or intermittent fasting, calls for restricting the calories you eat several days per week, while eating what you want on your non-fast days. The notion behind this diet is that it’s easier to starve yourself every other day, or perhaps even less often, than to do it every day. And if it’s easier, you’ll be more apt to stick with it.
As it turns out, that’s apparently not the case.
In a recent study comparing intermittent fasting with daily calorie restriction for weight loss, people in the intermittent fasting group were less likely to follow their eating plan carefully and more likely to quit it. On top of that, other studies have shown that intermittent fasters often exceed their calorie limits on fasting days.
Short-term vs. long term
Calorie restriction in general is an effective way to lose weight in the short-term. It can be a "jumpstart" of sorts, leading to significant weight loss over a period of weeks to months.
But calorie restriction alone is not a long-term weight solution and studies consistently show that most people don’t stick with it for life. It is extremely difficult to be hungry forever.
If you choose to trigger short-term weight loss with calorie restriction, it is crucial during that time to focus on improving your taste preferences, addressing your "food environments" and your habits, and making better food choices. You’re not going to starve yourself forever so this will help set you up for long-term success.
Helpful or harmful?
Weight loss can produce some powerful health benefits, such as improving blood pressure and metabolic health and lowering cholesterol. It may reduce joint pain and boost your energy.
And though in some studies, intermittent fasting appears to offer slightly greater health benefits, the evidence isn’t convincing. For example, some but not all studies have shown there is less loss of "fat-free mass," or lean muscle tissue, with intermittent fasting. Some have shown slight improvements in metabolic health compared to continuous calorie restriction. But it is difficult to know if these effects are reliable.
It appears there are few adverse effects of intermittent fasting. People on medications, particularly diabetes medications, should talk to their doctor before embarking on any calorie restriction program. Because calories equal energy, significantly restricting them can lead to relatively minor issues like headaches, lack of energy, bowel movement changes and feeling cold.
Should you try it?
Various forms of fasting have been used therapeutically, to good effect, for thousands of years, in a variety of different cultures and traditions. And while it appears there are more health benefits than risks to fasting, I strongly suggest discussing it with your doctor before you begin any serious calorie reduction program. This is even more crucial if you’re on medications or you have any significant medical conditions. People with a history of eating disorders should probably avoid regimented calorie control programs like this.
It's worth restating that any short-term calorie restriction program must be partnered with a long-term plan for weight maintenance, involving changing many aspects of life beyond counting calories. If your overall food choices and preferences don’t change, calorie restriction of any type—continuous or intermittent—will most likely result in yo-yo dieting, repeatedly losing and regaining weight. Yo-yo diets may have long-term harms. A recent study associated yo-yo dieting with an increased risk of sudden cardiac death. In addition, yo-yo dieting can alter metabolism in detrimental ways.
If your doctor gives the go-ahead and you’re determined to give it a try, design your intermittent calorie restriction around your lifestyle and your schedule. Try to incorporate some exercise. Most importantly—and this is crucial—focus on making long-term lifestyle changes right out of the gate. Change the food you do eat, choosing unrefined plant-based foods and meals. Think about your environment and how that supports or hinders healthy habits. If you eat all the same foods and do the things that got you into trouble in the first place, but just try to eat less or eat smaller portions, I'm concerned this will be a short-term, yo-yo diet.
You want to get to a point where you are enjoying healthier habits and eating healthier foods so that, when you stop starving yourself (and if you're like 99 percent of all people, you'll tire of starving yourself soon enough), you can maintain or even continue your weight loss with your new foods and habits, even though you're back to eating full meals whenever you're hungry.
Thomas M. Campbell, M.D., is medical director of the UR Medicine Program for Nutrition in Medicine. Participants in this program do not restrict or count calories and, in general, lose 1-2 pounds a week and reduce their blood pressure, blood sugar and cholesterol by eating as much as they want, whenever they want to avoid hunger. This is achieved by restricting food choice, avoiding processed foods and animal-based foods to satisfy hunger and still lose weight, without starving or counting anything, which can be more sustainable in the long run.