Can High-Fat Diets Help You Lose Weight Quickly?

Have you ever noticed how potato chips are so much lighter than potatoes? That’s because they let go of a lot of water in the cooking process. If all you want to do is shed pounds quickly regardless of where they come from, make like a potato chip and drop the water weight. It does the trick, right?

But that’s just it; it’s a trick. And it works on a high-fat diet because all that fat leaves little room for carbohydrates, which naturally hold water in the body. The latest high-fat diet to earn its moment in the spotlight is the ketogenic diet, which is so low in carbs that the body starts to convert fat into ketones for energy. Eat little to no carbs, and you can say goodbye to all the water they would have been stored with. This kind of weight comes back when carbohydrates are reintroduced into the diet. And, for the record, water is a good thing.

That doesn’t mean high-fat diets don’t have their merits. They typically cut out added sugar and refined grains, which should be healthy eating goals for all Americans. And while the average person really shouldn’t be on a ketogenic diet long term, according to Kristen Mancinelli, M.S., R.D., author of The Ketogenic Diet: A scientifically proven approach to fast, healthy weight loss, she does think that most people can try it for three months, and will see a huge difference in weight status. After the three months, Mancinelli advises slowly adding carbs back in as part of a well-rounded whole foods diet.

According to Mancinelli’s book, the amount of daily carbs one can consume to maintain ketosis depends a little bit on the person’s metabolism and more on where that person is on the weight-loss journey. She writes that most people spend their first month on the diet eating 20 grams of carbs or less per day, and can gradually increase the daily amount to 30 grams — but not to exceed 50 grams per day.

“A person who is scared of consuming too much fat and can’t control carb intake won’t be successful on a ketogenic diet,” says Mancinelli.

Very Short-Term Impact of High-Fat Diets

To get started, Mancinelli notes that all sugar and starch foods are removed: no fruit, grains, starchy vegetables, flour, bread, beans, rice, etc. She says you will also cut back on non-starchy vegetables like salad greens, brassicas (such as kale, broccoli, and cauliflower), leafy greens, and summer squash.

It’s easy to see why Mancinelli wouldn’t want these healthy foods off the plate forever. But while they are being restricted, Barry Sears, Ph.D., president of the Inflammation Research Foundation, warns that the diet will be low in: “fermentable fiber and polyphenols that are found in non-refined carbs,” which are essential to gut health.

Other start-up bummers can include constipation due to not a lot of fiber, muscle cramping due to potassium losses, and low energy due to the restricted amount of carbs. At a minimum, the brain needs approximately 120 grams of glucose per day. When this isn’t present, the brain is forced to use ketone bodies for energy.

There’s also preliminary data on short-term effects on muscle glucose metabolism. A very small study in 12 non-obese young men tested a high-fat diet for five days and found that it disrupted the way muscles used glucose. Researchers concluded that even in the short term, a high-fat diet may possibly lead to insulin resistance.

Two things to note: The amount of saturated fat consumed by the study participants was pretty high (at least 25 percent of the total 55 percent of daily calories from fat came from saturated fat), and this study had a very small sample size; more research would need to be done to validate findings.

It should be noted that there are high-fat diets that include all fats, and there are high-fat diets that emphasize healthy fats, such as avocados and wild fatty fish. Mancinelli confirms that not all high-fat diets are equal, “A diet high in poor-quality carbs and high in saturated fat is a sure way to raise heart disease risk, and should be avoided.”

Long-Term Impact of High-Fat Diets

Over a few months time, “high intake of saturated fat increases cholesterol levels, which can increase risk of heart disease; but, increased intake of monounsaturated fat reduces heart disease risk, so it’s tough to find a clear verdict here,” says Mancinelli.

On the other hand, she counters herself by noting that heart disease risk is closely linked to inflammatory markers, which are higher in overweight individuals, “so if a high-fat diet produces weight loss for an individual that a low-fat diet could not, then the benefits may outweigh the risks for that individual.”

Sears explains that when fat tissue is mobilized to form ketones, the body eventually responds by increasing the secretion of cortisol to break down existing muscle to make adequate levels of glucose for the brain. “It makes no sense to destroy muscle to make glucose for the brain when an adequate amount of carbs in the diet will have the same goal without the loss of muscle mass,” he says.

If you want to shed pounds and get healthier, too, then you need to focus on fat loss, not just weight loss, says Sears. “The clinical data is very clear that the fat loss is no greater on high-fat diets than lower-fat diets,” he says.

A study published in the American Journal of Clinical Nutrition suggests that when protein and calories are the same, a higher-fat diet has no benefits compared to a lower-fat diet. In fact, the study found that cutting back on calories in a moderate-fat diet led to more overall weight loss and fat loss than a calorie-restricted high-fat ketogenic diet.

The 10-Second Takeaway

Ultimately, there is more than one way to lose weight healthfully, and at varying levels of fat intake. A relatively higher-fat diet where fat makes up 35 percent of calories may be easier to stick to since fat carries so much flavor. Ultra high-fat diets, on the other hand, don’t seem to be great long-term solutions, and should be approached hand-in-hand with a qualified health professional.