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Low-Fat Diet: Facts, Benefits & Risks

salad, low-fat diet
A low-fat diet may be useful for short-term weight loss, but they may not be healthy in the long-term. (Image credit: llaszlo | Shutterstock)

Low-fat diets are diets that dramatically limit the grams of fat a person is allowed to consume throughout the day. Low-fat diets, though useful for short-term weight loss, may not be healthy or successful in the long-term, experts say.

Low-fat diets can help to lose weight, but it is more important to make healthy choices, not just limit fat intake, according to Dr. Dana S Simpler, an internist that practices in Baltimore, Maryland. “If you replace fat with chocolate syrup or sugared beverages, you will not achieve good health or successful weight loss," she said. "However, if you substitute beans for steak at dinner and use a flavored vinegar instead of oil and vinegar on your salad — yes, this is a healthy weight loss strategy.”

Though a person can lose weight with a low-fat diet, it may not be the best choice of diet. When compared with low-carb diets in many studies, study participants typically lost more weight with a low-carb diet and reaped much more health benefits, such as significant reductions in blood triglycerides, than with a low-fat diet. Low-carb or low-fat doesn’t matter as much as how many calories are consumed in a day, according to the Mayo Clinic. As long as calorie intake is lowered, then a diet will more than likely help a person succeed in losing weight. 

Benefits of a low-fat diet

The benefits of a low-fat diet are much contested and many studies have found very little, if any benefit. For example, an eight-year trial of almost 49,000 women, called the Women’s Health Initiative (WHI) Dietary Modification Trial, found that a low-fat diet had no effect on breast cancer, heart disease, colorectal cancer or weight. A study published in the October 2015 issue of the journal The Lancet Diabetes & Endocrinology, found that low-fat diets are also of no use for long-term weight loss. 

On the other hand, another study found that limiting fat intake can help limit hot flashes during menopause. 

Risks of a low-fat diet

Several of the experts Live Science contacted for this article said they would not recommend a low-fat diet. This is because the body needs fat. “If you eliminate fat too much, it can have serious health consequences," said Jennifer Fitzgibbon, a registered oncology dietitian at Stony Brook Hospital Cancer Center in New York. "Mental health deficits like depression and vitamin deficiencies can occur. The vitamins A, D, E and K are fat soluble, meaning the body stores them in fatty tissue and the liver. The intestines need dietary fat to properly absorb these nutrients. These vitamins are also necessary for the health of your skin, bones and cardiovascular system, among other organs and systems,” 

Also, some fats are very healthy. For example, omega-3 fats from fish, flaxseeds and walnuts have many health benefits. Other “good fats” include monounsaturated fats found in extra virgin olive oil, olives, avocadoscoconut oil, nuts and seeds, according to the University of Michigan. Other fats may not be so bad, either. “Interestingly, it appears more and more that perhaps saturated fats like butter, cream and other types coming from animals are not as harmful as we once thought," said Liz Weinandy, an outpatient dietitian at the Ohio State University Wexner Medical Center. "We will have to let science sort that out and we'll know more in the next few to several years."

How much fat should be cut?

There are limits for cutting fat. According to Fitzgibbon, dietary guidelines suggest healthy adults should generally limit dietary fat to no more than 20 to 35 percent of total daily calories. So if someone's diet plan calls for eating 2,000 calories a day, 400 to 700 calories can come from dietary fat (fat = 9 calories per gram), which translates to between 44 and 78 fat grams a day. Dietary guidelines set by the American Heart Association and the National Cholesterol Education Program recommend restricting consumption of fat to an upper limit of 30 percent of daily caloric intake. Using the Nutrition Facts label is the best way to find out how much fat is in foods. 

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Alina Bradford
Alina Bradford
Alina Bradford is a contributing writer for Live Science. Over the past 16 years, Alina has covered everything from Ebola to androids while writing health, science and tech articles for major publications. She has multiple health, safety and lifesaving certifications from Oklahoma State University. Alina's goal in life is to try as many experiences as possible. To date, she has been a volunteer firefighter, a dispatcher, substitute teacher, artist, janitor, children's book author, pizza maker, event coordinator and much more.