Low Fat VS Low Carb (which loses more body fat?)

Key Takeaways

• The best diet is the one you can stick to
• A low fat diet leads to more body fat loss than low carb, even though eating low carb burns more fat to meet energy needs
• In the long term, any diet that restricts calories to similar levels, leads to similar amounts of body fat loss

A study from the US National Institutes of Health presents some of the most precise human data on whether cutting carbs or fat has the most benefits for losing body fat.

Kevin Hall, PhD has been using data from dozens of controlled feeding studies conducted over decades of research to build mathematical models of how different nutrients affect human metabolism and body weight.

He noticed that despite claims about carbs versus fat restriction for weight loss, nobody had ever measured what would happen if carbs were selectively cut from the diet while fat remained at a baseline or vice versa.

His model showed that only the carb-restricted diet would lead to changes in the amount of fat burned by the body

A reduced fat diet would lead to greater overall body fat loss, but he needed the human data to back it up.

"A lot of people have strong opinions about what matters for weight loss, and the physiological data upon which those beliefs are based are sometimes lacking," Hall says.

"I wanted to thoroughly test the theory that carb restriction is particularly effective for losing fat since this idea has been influencing many people's decisions about their diets."

The Study

Studying the effects of diet on weight loss is often confounded by the difficulty in measuring what people actually eat.

To counter this, Hall confined 19 consenting adults with obesity to a metabolic ward for a pair of 2-week periods. Over both 2 week periods every morsel of food eaten was monitored and controlled.

To keep the variables simple, the two observation periods were like two sides of a balance scale: during the first period, 30% of baseline calories were cut through carb restriction alone, while fat intake remained the same. During the second period the conditions were reversed.

Each day, the researchers measured how much fat each participant ate and burned and used this information to calculate the rate of body fat loss.

Result found that

At the end of the two dieting periods, the mathematical model proved to be correct.

Body fat lost with dietary fat restriction was greater compared with carbohydrate restriction, even though more fat was burned with the low-carb diet.

"There is one set of beliefs that says all calories are exactly equal when it comes to body fat loss and there's another that says carbohydrate calories are particularly fattening, so cutting those should lead to more fat loss," Hall says.

"Our results showed that, actually, not all calories are created equal when it comes to body fat loss, but over the long term, it's pretty close."

Hall does caution against making sweeping conclusions about how to diet from this study.

The study's purpose was to explore the physiology of how equal calorie reductions of fat versus carbs affect the human body.

Study limitations

The research is limited by its sample size; only 19 people could be enrolled due to the expense of such research and the restrictiveness of the carefully controlled protocol.

In addition, the menu that the participants followed does not emulate normal dieting and does not account for what diet would be easier to eat over extended periods.

"But there is currently a gap between our understanding of the physiology and our ability to make effective diet recommendations for lasting weight loss."

Hall recommends that for now, the best diet is the one that you can stick to.

A few little tips

Make sure to keep an eye on your body fat by regularly checking your BMI and measuring your waist! 

Check out our Low Fat Diet Report to find out how you can reduce fats from your diet.

Our plans are low fat in nature so head over to our large choice of weekly diet plans for a variety of diets to try out!