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The Low-Fat Diet: History, Myths, and Truths

I was recently in Nashville celebrating Christmas with my family. My mother and I were looking through all the cupboards for our favorite holiday cookie recipe, peanut butter blossoms. It’s an old favorite passed down from many generations. As we searched, we stumbled upon diet book after diet book stacked in the back of one cupboard, promoting low-carb diets, low-fat diets, and more. Most of them were at least 30 years old. I kindly asked my mom if I could trash the books, but she decided to put them back in the cupboard to collect dust for another 20 years. You know moms and their collections! I let it go, but it got me thinking about these decades-old diet books and what they might have led my mom to believe about dietary fats all those years ago…

There’s power in knowing the history, so let’s start there. Scientists began promoting the “low-fat diet” in the 1950s. Their claims were loosely supported by an unproven hypothesis called the “diet-heart hypothesis,” which predicted that diets high in saturated fats and cholesterol were a major cause of coronary heart disease. Although these scientists acknowledged there was no concrete proof that a low-fat diet could prevent heart attacks or strokes, their claims were just as widespread as one with supporting evidence might be.

The original low-fat diet was initially only recommended for high-risk cardiac patients, but this didn’t last long. Starting in 1984, despite a lack of evidence supporting the diet-heart hypothesis, federal health policies, healthcare practitioners, and the media announced the low-fat diet as a way to prevent heart disease for all. Of course, the diet industry quickly got ahold of this information and began spreading it to the masses – at that time, 86% of women received health advice from magazines, so it was easy to promote the low-fat diet to large audiences.

This history only provides a small glimpse into all the politics, money, and weak evidence associated with the low-fat diet. Instead of putting more energy into the unsupported claims made about this eating pattern, let’s focus on the benefits of dietary fat and bust some myths along the way.

1. Low-fat leads to hunger.

Dietary fats promote fullness and satiety, which is defined as “the state of non-eating, the absence of hunger.” Fats are digested more slowly than carbohydrates and proteins, allowing us to feel full and satisfied for longer after a meal. By restricting our fat intake, we’re left feeling physically hungry and psychologically unsatisfied at the end of a meal. As a result, we can end up making impulsive food choices or reaching uncomfortable fullness levels in an attempt to feel satiated.

2. Low-fat leads to low energy levels and low endurance.

If you read our blog post about the low-carb diet, you learned that carbohydrates give us energy that not only fuels our basic bodily functions, but also fuels any forms of exercise and movement that we do. Dietary fat is a critical source of energy as well, it’s just used in a different way than carbs. Fat is utilized by our bodies for slower, longer, lower-to moderate-intensity/endurance exercises, such as distance running, walking, or cycling. Inadequate intake of dietary fats can therefore negatively impact athletic performance during these types of movement.

3. Low-fat leads to a long list of replacements.

Many consumers believe that low-fat products are a better choice. In the 1980s, once food producers realized they could make a profit off of America’s desire for low-fat products, they began replacing fat with sugar in processed foods. In some cases, these “low-fat” versions of snack foods and sweets had as many calories as the original versions. Low-fat and fat-free products don’t just take away fat; they add sugar, preservatives, artificial food dyes, and other additives to make up for the removed flavor. But because this isn’t advertised, people often eat relatively larger quantities of diet foods, because they perceive them to be “lighter” or “healthier.” A phenomenon called the Snackwell’s effect describes this tendency for dieters to eat more when they’re consuming low-fat versions of food, compared to the original versions.

4. Low-fat means low vitamin absorption.

Dietary fat helps the body to absorb fat-soluble vitamins (A, D, E, and K). These vitamins are essential for protecting vision, strengthening immune function, healing wounds, and building bones. In order for these valuable nutrients to be absorbed from our intestines and released into the bloodstream, we need fats to be present. In addition, fats make up 60% of the human brain and support various functions in our bodies, including wound healing, blood clotting, hormone production, temperature regulation, and immune responses. Fats support our overall health.

5. Low-fat lacks omega-3 and omega-6 fatty acids.

These are both essential fatty acids, meaning our bodies need them to function properly but cannot produce them using the body’s own resources. We have to obtain these fatty acids from our diets in order to enjoy their health benefits. Omega-3 fatty acids are found in salmon, fish, flax seeds, chia seeds, walnuts, eggs, meats, avocado, canola oil, and dairy. Consuming omega-3s offers a multitude of health benefits, including reduced risk of heart disease, stroke, and depression; reduced inflammation and blood pressure; reduced severity of ADHD symptoms; and increased protection against Alzheimer’s disease and dementia. Omega-6 fatty acids are found in walnuts, almonds, eggs, hemp seeds, sunflower seeds, peanut butter, cashews, avocado oil, and tofu. Omega-6s improve cholesterol levels, keep blood sugar stable, stimulate hair and skin growth, maintain bone health and reproductive health, and regulate metabolism.

It should be noted that people with specific medical conditions may need to watch their saturated fat intake, but for the average individual, there is no significant association between saturated fat intake and health outcomes. Dietary fat can and should be consumed regularly to promote its associated health benefits. As with any other nutrient, sources of dietary fat should be consumed in moderation, as part of a balanced, varied diet that includes sources of all other food groups as well.

Fad Diets: Same Mechanism, Different Name

Do you notice a trend here? Medical advice initially prescribed by physicians for high-risk heart disease patients, then marketed by the mainstream media as a new way to lose weight… Sound familiar? It’s exactly how the low-carb diet came about too, and I don’t see the media stopping this trend any time soon. The truth is, there’s nothing magic about the low-carb and low-fat diets; they promote weight loss through restriction of caloric intake, the same way all other diets do. When you reduce or eliminate an entire macronutrient from your diet, it generally means you’re eating less overall, and you enter a calorie deficit that ultimately leads to weight loss. And because dietary fats are more energy dense per unit volume than other nutrients, the media was quick to teach that reducing fat intake was an effective way to lose weight. But just like any other diet, the low-fat diet isn’t sustainable, and we now know that restricting dietary fats has a multitude of associated health consequences.

If only my mom could have known all of this when she was trying out the trendy new low-fat diet in the 1980s! But despite all the research that has since been conducted on the consequences of dieting, the scientific facts can get convoluted, manipulated, or even ignored in today’s world, especially on social media platforms that have become a top source of nutrition information. By learning about the health benefits of consuming dietary fats and other demonized nutrients, and the dangers of restricting them, we can start to shift the narratives that have spread misinformation for decades.

Written by Kayla Burson, nutrition volunteer at Restore Family Therapy

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