What to know About Low-Fat Diets

A creamy peanut butter in a bowl next to unshelled peanuts.Sep 1, 2023

By: Kelsey Lorencz, RD

Low-fat diets have been around for decades, often advertised as a way to lose weight or improve your heart health. But what is a low-fat diet and how does it relate to your health?

What is Dietary Fat?

There are four types of fat we get from the food we eat: saturated, trans, polyunsaturated and monounsaturated. Saturated and trans fats are solid at room temperature while the unsaturated fats remain liquid at every temperature.

The American Heart Association supports replacing saturated fats and trans fats with healthier, unsaturated fats (1). Saturated and trans fats have been shown to increase LDL-Cholesterol levels in the body. Unsaturated fats can have the opposite effect when part of a healthy diet, lowering LDL-cholesterol and triglycerides, reducing the risk of heart disease (2), (3). Rather than limiting total fat, it is important to include more of the healthy unsaturated fats and less saturated and trans fats in your diet (4).

Using olive oil instead of butter and replacing meat with plant-based options, such as peanuts, seeds, soy and avocado is a great place to start.

Low-Fat Diets Can Raise Triglycerides and Lower HDL (the good cholesterol)

Studies consistently find that very low-fat diets (less than 15% of total calories from fat) result in elevated triglycerides and lower HDL (the good cholesterol) (5). The reason behind this is not exactly clear, but we do know that high triglycerides and low HDL are both predictors of heart disease (6).

Increased Nutrient Deficiency

Our bodies need fat for insulation, energy and brain development, as well as for healthy and hydrated hair and skin (7).

Many nutrients are absorbed and used more efficiently when they are eaten along with dietary fat. The fat-soluble vitamins A, D, E and K all require fat for absorption.

A small 2015 study of 50 participants was published in the Journal of the Academy of Nutrition and Dietetics tested if the absorption of vitamin D-3 is greater when the supplement is taken with a meal containing fat than with a fat-free meal and that absorbtion is greater when the fat in the meal has a higher monosaturated-to-polysaturated fatty acid ratio. The study found that taking a vitamin D supplement with a meal containing dietary fat resulted in plasma vitamin D levels 32% higher than those who ate a fat-free meal with their supplement, but the monosaturated-to-polyunsaturated fatty acid ratio in that meal does not influence is absorption (8).

Some limitations of the study included that further work is needed to determine whether absorption of vitamin D from smaller doses is similarly affected by meal content, and whether, with repeated dosing, absorption remains the same. This study provides the rationale for recommending that vitamin D supplements be taken with a meal containing fat (8).

In addition to vitamin absorption, we need essential fatty acids for brain development, controlling inflammation and blood clotting (7). These essential fatty acids are known as omega-3 (linoleic) and omega-6 (linolenic) fatty acids.

Essential nutrients are ones that we can’t make on our own and need to get through our diets. Eating fish and plant sources of fat like seeds and nuts can provide all the essential fatty acids we need.

Peanuts and Dietary Fat

A 1 ounce serving of peanuts contributes:

  • 14g of total fat
  • 7 grams of monounsaturated fats
  • 5 grams of polyunsaturated fats
  • 2 grams of saturated fat

Scientific evidence suggests but does not prove that eating 1.5 ounces per day of most nuts, including peanuts, as part of a diet low in saturated fat and cholesterol may reduce the risk of heart disease.

Put your peanuts to work by pairing them with fat-soluble vitamin sources to maximize absorption!


  1. “Dietary Fats.” Www.Heart.Org, 10 May 2023, https://www.heart.org/en/healthy-living/healthy-eating/eat-smart/fats/dietary-fats
  2. Forouhi, Nita G, et al. “Dietary fat and cardiometabolic health: Evidence, controversies, and consensus for guidance.” BMJ, 13 June 2018, https://doi.org/10.1136/bmj.k2139.
  3. “The Truth about Fats: The Good, the Bad, and the in-Between.” Harvard Health, 12 Apr. 2022, https://www.health.harvard.edu/staying-healthy/the-truth-about-fats-bad-and-good.
  4. “Fats and Cholesterol.” Harvest T.H. Chan School of Public Health, 22 May 2019, https://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/fats-and-cholesterol/.
  5. Lichtenstein, Alice H., and Linda Van Horn. “Very low fat diets.” Circulation, vol. 98, no. 9, Sept. 1998, pp. 935–939,https://www.ahajournals.org/doi/full/10.1161/01.cir.98.9.935
  6. “ABCs of Knowing Your Heart Risk.” Johns Hopkins Medicine, 20 Dec. 2022, https://www.hopkinsmedicine.org/health/wellness-and-prevention/abcs-of-knowing-your-heart-risk
  7. “Dietary Fats Explained: Medlineplus Medical Encyclopedia.” MedlinePlus, U.S. National Library of Medicine, 30 July 2023, https://medlineplus.gov/ency/patientinstructions/000104.htm
  8. Dawson-Hughes, Bess et al. “Dietary fat increases vitamin D-3 absorption.” Journal of the Academy of Nutrition and Dietetics vol. 115,2 (2015): 225-230. https://pubmed.ncbi.nlm.nih.gov/25441954/

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