Low-Fat Vs. Low-Carb: When It Comes to Weight Loss, Science Has a Winner

In this corner, weighing in at 170 calories, 0 grams of fat, and 37 grams of carbohydrates: the russet potato! And in this corner, weighing in at 200 calories, 12 grams of fat, and 0 grams of carbohydrates: sirloin steak! Who will win this controversial heavyweight match-up? 

Remember that decades long obsession with low-fat dieting? Then the new millennium brought the breakthrough of going low-carb for weight loss. The debate goes back and forth even today—healthy fats are in and carbs, still kind of evil . . . until now.

There’s good news for those not willing to give up sandwiches and rice bowls—recent research has discovered that cutting fat is slightly more effective for losing weight than cutting carbs. Does this mean dieters everywhere can break out the linguine? Well, maybe not.

So how exactly did this go down? The National Institutes of Health confined 19 obese human research subjects in a tightly controlled lab, strictly regulating their diets. They ate a balanced diet for five days, and they were switched to either a low-fat or low-carb diet, each with a 30 percent decrease in caloric intake. They did this for six days, broke for a few weeks, and then did it again, switching each subject to the opposite diet.

In the end, the low-fat diet caused a loss of 463 grams of fat on average—the low-carb diet, 245 grams. Not only did the low-fat group lose more weight, but they lost more body fat as well. Researchers projected that on low-fat, people would lose over six pounds more than on low-carb over the next six months. Not a huge number, but still enough to reconsider that cutting carbs is the definitive way to lose weight.

Although maintaining a healthy weight can help prevent inflammation as well as certain diseases like heart disease, obesity, diabetes, dementia, depression, and cancer, overall health isn’t all about dropping pounds. Paleo eaters who eat a healthy high-fat diet of animal protein and omega-3 fats experience improved digestive health, more muscle mass, reduced inflammation, and high energy.

If weight loss is the goal, worry about regulating calories rather than fat or carbs. Both low-fat and low-carb can help achieve this. A good rule of thumb is to load up on fresh vegetables, fruits, lean protein, omega-3 fats from nuts and seeds, and if you want, low-glycemic grains and legumes.

So the takeaway is not that eaters should drop the steak and fill up on baked potatoes instead—as always, balance is key. Heaping plates of spaghetti and meatballs probably won’t slim anyone down. Binging on high-glycemic foods like potatoes, white bread, bagels, and white rice can still lead to obesity, and natural sources of fats like coconut oil, avocado, and lean cuts of protein are still amazing, nutritious foods to keep on hand—in moderation.