Here’s The Best Online Calorie Tracker, According To Science

Want to lose weight, but don’t know where to start? A free online calorie calculator — the Body Weight Planner — is now available to the public after several years as a research tool for scientists at the National Institutes of Health.

There are plenty of free tools online to help you count calories in diet and exercise, but this one is noteworthy because its algorithms were validated in several controlled weight loss studies in human beings, notes a press release, and because it takes into account a person’s slowing metabolism.

Kevin Hall, a scientist at the NIH’s National Institute of Diabetes and Digestive and Kidney Diseases, created the tool. He demonstrated how the calculator works using his own weight loss goals as an example:

Hall, a 44-year-old man who wants to lose 20 pounds off his 5’10, 180-pound frame, is going to have to eat about 2,300 calories per day, provided he sticks to his resolution to walk his dog in the mornings three times a week. Once he reaches his goal weight, he’s going to have to maintain that weight loss by keeping up his dog-walking activity level and eating about 2,600 calories a day.

The NIH bills the planner as a cutting-edge tool that will empower people to take their health into their own hands, but research on the success of such calculators and trackers is mixed, according to Dr. Zhaoping Li, director at the Center for Human Nutrition at UCLA’s David Geffen School of Medicine. She praised the federal government for its official nod toward the utility of trackers and calculators, but, she noted, human beings themselves are not “simple machines” who operate on a calories in, calories out basis.