If you’ve ever tried to lose weight, you may have heard that a pound of fat equals 3500 calories. Put in practical terms, to drop a pound a week, you’d need to eat 500 calories less or burn 500 calories more per day. You may still come across this advice, but new research has disproved this rule of thumb, known as the 3500-calorie rule. Cutting 500 calories a day can lead to weight loss, but it may not be as much as that rule of thumb would predict.
Back in 2013, researchers decided to test the 3500-calorie rule. They looked at data from seven weight-loss studies where participants were closely monitored, often spending as long as 3 months in a research facility, 24 hours a day. In these studies, most participants lost much less weight than the 3500-calorie rule predicted. In addition, they found that weight loss slowed as the weeks progressed. This fits with what many people experience when they try to lose weight – losing the first couple of pounds may be easy, but sooner or later, weight loss plateaus.
What happens as you lose weight – even a pound or two – is that your body needs slightly fewer calories. If you continue to eat the same amount that helped you lose those first few pounds, your weight loss will naturally slow because your calorie deficit will get smaller as your weight goes down. This can be discouraging, but by setting realistic expectations, being patient and combining physical activity with eating less, you can be successful.
The other problem with the 3500 calorie rule is that it assumes that everyone responds to the same calorie cut with equal weight loss. Research shows that is not true. The same decrease in calories leads to faster weight loss in men than women, and in younger adults than in older adults; and individuals within these groups also differ.
So you want to lose weight – now what?
Instead of basing your weight loss expectations on the 3500-calorie rule, use the National Institutes of Health’s free, online Body Weight Simulator to set more realistic goals. The simulator uses your height, current weight, sex and goal weight to estimate how much you should eat and how much weight loss you can expect over time.
Reducing your usual calorie intake by about 500 calories a day is still a recommended strategy for many people. Find ways to do it that you can sustain long term. And the key message now is not to be discouraged or think it’s “not working” if your weight loss does not meet the now-outdated one-pound-per-week expectation.
For cancer prevention and overall health, AICR promotes making small, everyday changes in diet and exercise as an effective way to lose weight. However, the extra physical activity and/or decrease in calories has to be permanent and it may take at least a year or more to reach your target weight. So choose changes you can stick with long-term (and be patient) rather than looking for quick fixes.
Enlist support from family and friends. Ask them to help and let them know specifically what they can do to support you. If you’re still unsure about how much you should be eating or how much weight loss to expect, consider making an appointment with a registered dietitian (RD) in your area for weight-loss counseling. The New American Plate Challenge, AICR’s RD-staffed online weight-management program is another great resource for guidance, tips, and support throughout your weight-loss journey.