What Is a Low-Fat Diet?

In This Article
Apple and cupcake on contrasting faces
Gary Waters/Ikon Images/Getty Images

Low-fat diets, in which calories from fat sources are cut dramatically, were once considered the best way to reduce body fat and lower the risk of heart disease and even cancer. Today, we know more about how dietary fat affects the body. Recommendations now center on promoting some fats while limiting others.

What Experts Say

"Low-fat diets were popular in the past for heart health, but we’ve learned more about them over time. Not all fats are created equal. There are healthy fats, like what we find in avocados and olive oil, and unhealthy fats—saturated and trans fats—which we should limit."
Kelly Plowe, MS, RD

Background

Beginning in 1977, both the U.S. government and the American Heart Association (AHA) began urging Americans to limit the amount of fat they consumed in their diet. This recommendation was based on the theory that because eating saturated fats increases cholesterol levels, reducing fat consumption would lower the risk of atherosclerotic cardiovascular disease.

However, the scientific evidence that strictly limiting dietary fat lowers the risk of atherosclerosis is (and always has been) quite weak, and the recommendation was quietly dropped in 2010.

Even in 1977, scientists knew that not all fats are “bad,” and indeed that certain fats are essential for good cardiovascular health. But the McGovern Commission (the committee which published the first edition of "Dietary Goals for the United States") was determined to limit all fat intake, both to reduce heart disease and (it was incorrectly assumed) to fight obesity. They feared they would just confuse the public by trying to convey a relatively complex message that most fats should be avoided, but some fats are desirable. So, the official message became to avoid fats altogether, and instead to rely largely on carbohydrates for the majority of our caloric intake.

How It Works

In general, a low-fat diet is one in which no more than 20 to 35 percent of daily calories come from any fat source. An updated take on this would be to cut out trans fats and reduce intake of saturated fats, while still consuming unsaturated fats.

What to Eat

Compliant Foods

  • Carbohydrates

  • Protein

  • Heart-healthy fats (in moderation)

Non-Compliant Foods

  • Saturated fats (in excess)

  • Trans fats

Carbohydrates

Carbs are a necessary source of energy, and you'll find them in healthy, nutritious foods: fruits, vegetables, and whole grains. But if you're looking to lose weight, be careful not to replace fats with "low-fat" foods that are actually high in sugar and refined flour (which are also carbohydrates).

Protein

Like fats, proteins help you feel full, so be sure to consume plenty of protein-rich foods. But to keep your diet lower in fat, choose lean protein sources such as legumes, fish, skinless poultry, and lean cuts of beef.

Heart-Healthy Fats

There are two kinds of unsaturated fats, and both are thought to help lower LDL (or "bad") cholesterol levels.

  • Monounsaturated fats, sometimes called MUFAs, come from plant sources, such as avocados, olives, and nuts. These fats are usually liquid at room temperature (think olive and canola oil).
  • Polyunsaturated fats, or PUFAs, are found in nuts, seeds, and fish, and are a good source of vitamin E and omega-3 and omega-6 fatty acids.

Saturated Fats and Trans Fats

Saturated fats are found in animal products, such as meat, butter, and cream, and a few plant sources, including coconut and palm oil. Trans fats are unsaturated fats that have been processed to make them more shelf-stable. They usually show up on food labels as "hydrogenated" or "partially hydrogenated" oils. While baked goods and other commercially prepared products in the U.S. are not allowed to contain trans fats (as of June 2018), they can still be found in fried foods.

Trans fats should be avoided altogether, both for general health and especially on a low-fat diet. Saturated fats are hard to avoid unless you do not consume animal products, but you can limit them by choosing lean proteins and low- or non-fat dairy products.

Pros and Cons

Pros

  • Short-term weight loss

Cons

  • Little evidence of health benefits

  • Restrictive

  • Mental health risks

Pros

Short-Term Weight Loss

If you make an effort to reduce your fat intake, it is likely that you will lose weight. This holds true for most diets that restrict a certain type of food or macronutrient (such as carbohydrates). However, to keep this weight off, you will need to continue limiting fat in your diet.

A low-fat diet is likely to be healthy and may help you lose weight if it is still balanced with "good" fats and nutrient-rich carbohydrate and protein sources. But there are drawbacks to be aware of, most notably the change in expert advice regarding fat consumption.

Cons

Lack of Scientific Evidence

The 20-year Nurses Health Study, involving 80,000 women, showed no correlation between the risk of heart disease and dietary fat. A subsequent meta analysis of several studies similarly showed no association between dietary fat and heart disease or death.

In the most rigorous trial ever conducted to study dietary fat, the Women’s Health Initiative randomized over 48,000 women to a low-fat diet or a control group. Those in the low-fat group received intense behavior modification to reduce their daily fat intake to 20 percent of total calories and to increase consumption of grains and vegetables. The control group received only “usual” dietary education and consumed 37 percent of their diet from fat. After eight years, there was no reduction in the risk of coronary artery disease (CAD) in the low-fat group. In fact, the trend was for higher risk.

Other randomized trials have similarly failed to show a heart-health benefit to a low-fat diet. Additional studies have failed to show a reduced risk of cancer with low-fat diets, or that low-fat diets are associated with less obesity. Research is ongoing into the benefits of a very low-fat diet (less than 10 percent of calories from fat).

Restrictive

Some important vitamins (including vitamins A, D, E, and K) are fat-soluble, which means your body can't use them unless you are consuming dietary fat. So cutting out too much fat means your body won't be able to absorb these important nutrients.

Mental Health Risks

Dietary fat (meaning fat your body gets from food) is important for brain health and development. In particular, some research has shown that fatty acids from unsaturated fats might protect against depression.

How It Compares

"Low-fat diet" is a broad term, and advice has changed over the years, making it difficult to compare these diets to each other. Guidelines from the government and the AHA no longer specify a low-fat diet, but still recommend severely limiting saturated fats and using low-fat dairy products. Many experts now recognize other diets, such as the DASH diet, as heart-healthy choices.

USDA Recommendations

In February 2015, the Dietary Guidelines Advisory Committee (the group that reviews nutritional science every five years on behalf of the U.S. government), published its latest report stating that “dietary advice should put the emphasis on optimizing types of dietary fat and not reducing total fat.”

Similar Diets

The Ornish diet, and other variants of ultra-low fat diets, claim to not only prevent CAD but also to reverse it. These diets are far more rigorous in their restriction of dietary fats—especially from animal sources—than are the low-fat diets recommended by the AHA. Proponents of Ornish-type diets correctly claim that the studies that have failed to show a benefit with AHA-type diets do not necessarily apply to their far more fat-restrictive diets.

However, the claims that Ornish-type diets are proven effective are themselves based on imperfect data that does not hold up well to objective scrutiny. The hypothesis that a very-low-fat vegetarian diet prevents or reverses heart disease has been neither convincingly proven nor disproven, although it is a hypothesis that deserves more study.

Other diets that are balanced nutritionally, lower in saturated fats, and recommended by experts include the Mediterranean diet, the pescatarian diet, and the DASH diet (DASH stands for Dietary Approaches to Stop Hypertension).

A Word From Verywell

The recommendation that everyone should eat a low-fat diet was from the beginning based on a flawed theory, and on a conscious decision to sacrifice precision for the sake of simplifying the message. After more than three decades of attempting to confirm that low-fat diets reduce heart disease, clinical trials did not support longstanding recommendations that everyone should be on a fat-restricted diet. If you are looking to lose weight, consult your doctor to help design a plan that works for you. For heart health, consider the Mediterranean or DASH diets.

Was this page helpful?

Article Sources

Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial policy to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.