What Is a Low-Fat Diet?

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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, more is known 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

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

Background

The U.S. government has been providing dietary guidance for Americans for many years. The first edition of The Dietary Goals for the United States was published in 1977.

Dietary guidance has generally included advice about what to eat and drink for better health, but the specific messaging has changed throughout the years to reflect advances in nutritional understanding and the role of specific foods and nutrients on overall health.

The earliest guidance focused specifically on reducing how many people had diet-related diseases, such as cardiovascular disease and diabetes. Fat was identified as the primary culprit.

The guidelines, while well-intentioned, greatly influenced average Americans’ perception of a healthy diet. There was no distinction between "good" and "bad" fats. As a result, many people were avoiding otherwise-healthy foods based on their fat content alone.

Updated guidelines focus on finding a healthy balance of "good" fats and other important nutrients.

How It Works

In general, a low-fat diet is one in which no more than 30% of daily calories come from any fat source. On an individual food basis, the most-widely accepted definition of a low-fat food is one that has 3 grams of fat or less per 100 calories.

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, both of which 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, as well as 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

Unclear Scientific Evidence

Many studies have been conducted to determine the extent of health benefits for people following low-fat diets. Overarchingly, the evidence does not support low-fat diets over other dietary interventions for long-term weight loss.

Additionally, evidence has suggested that following unhealthy low-fat diets may actually be associated with increased risk of death.

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. Cutting out too much fat means your body won't be able to absorb these important nutrients.

Mental Health Risks

Dietary fat 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 one plan to another.

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 Dietary Approaches to Stop Hypertension (DASH) diet, as heart-healthy choices.

USDA Recommendations

In December 2020, the Dietary Guidelines Advisory Committee (the group that reviews nutritional science every five years on behalf of the U.S. government), published its latest guidelines outlining the appropriate amounts of daily nutritional intake, including fats, for people across different life stages.

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.

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.

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