Does Eating Fat Really Make You Fat?

By Catherine Roy, November 30, 2021

health impacts of eating fatAs the second chapter of our three-part National Heart Health Month series, we're talking about a topic that can sometimes confuse even the best of us: the difference between fat in our diets and fat in our bodies (and the implications of both on our health).

 The source of confusion

Throughout the 1960s and 70s, a few major reports said that reducing dietary fat was the single most important change that Americans could make for their health. And as a population, we were quick to get on board; it seemed logical to most people that eating less fat would mean losing body fat. As a result, the low-fat diet craze exploded onto the scene.1,2

Yet, despite these reports, obesity rates doubled from 20% in 1988 to a striking 40% in 2014.3 Why is this? Because fat alone does not make you fat. It’s eating or drinking more calories than you need, regardless of the source, that causes weight gain.

Since those original publications, dozens more have come out dispelling this low-fat craze, indicating that low-fat diets are no better than moderate or high-fat ones (in fact, for some people, they may be worse).

So, if dietary and body fat are different, how are they different? And perhaps more importantly, are they related? As usual, we have all the information for you and the science to back it up!


Dietary fat

Dietary fat is a vital macronutrient that is necessary and beneficial for health. It supplies us with lasting energy and helps our bodies absorb essential vitamins A, D, E, and K. Additionally, there are certain types of fat our bodies need that we can only get from our diet (keep reading, you’ll see what we mean).  

When it comes to dietary fat, type is arguably more important than amount. Choosing “good fats” and limiting  “bad fats” will be more beneficial to your health than adopting a low-fat diet.

The “good fats” include mono- and polyunsaturated fats like those found in fish, nuts, seeds, avocados and vegetable oils (olive, canola, corn, soy, sunflower). The “bad fats” are trans- and saturated fats. Fortunately, trans-fats have been almost completely eliminated from the food supply, but saturated fats are found in foods like butter, cheese, and red meat.

Diets high in mono- and polyunsaturated fats have been associated with beneficial effects, like a significant reduction in blood pressure, triglyceride levels, and body weight, along with a bump in HDL levels.4,5 Plus, remember those certain fats we mentioned earlier, that our bodies can only get from our diet? They're omega-3 and omega-6 polyunsaturated fatty acids.

However, even in the context of these unsaturated fats, we have to be wary of what and how we eat.

Multiple studies have found that eating a disproportionately high amount of omega-6s, compared to omega-3s, can cause inflammation.

Throughout most of human history, our omega-6 to omega-3 ratio was nearly 1:1. But because of how much processed food we eat, and how much omega-6-rich processed oil is in these foods, the Western diet has brought this average ratio closer to 16:1.6

While, yes, many people can benefit from eating more omega-3s, eating 16 times more than we currently do (to bring the ratio back to 1:1) is not the answer. Rather, focus on eating less omega-6s by eating less processed foods and harnessing cooking methods that don't require added fats, like roasting and steaming.


Body fat

Body fat is, well, the fat stored away in our bodies. It is also called adipose tissue. The main purpose of adipose tissue is to stash away excess energy (aka calories) to be used when your body needs it (like during exercise). Notice how we use the term “energy” here, and not “fat?” That's the major takeaway from this article: this storage process can happen when we take in too much energy of any kind – be it from protein, carbs, or fat. But just like dietary fat, not all body fat is created equally. 

Essential body fat, as the name implies, is essential for survival. It plays a significant role in your overall health, taking part in conserving body heat, protecting internal organs, and maintaining reproductive health.

Storage body fat is the fat that accumulates as a result of excess energy intake. The American College of Sports Medicine recommends 18-22% for men and 20-32% of total weight (ex. 30-50 lbs of fat for a 150 lb woman) as target ranges for good health. Certain scales, like this one, can measure your body fat percentage.

Storage fat can be further divided into two sub-categories: subcutaneous and visceral fat. Subcutaneous fat is the fat that is directly under our skin – it can be pinched, touched, and seen. This type of fat is usually what motivates people to lose weight, as it most directly impacts appearance.

On the other hand, visceral fat cannot be seen. It is stored deep beneath the skin and wraps around some of our major organs including the liver, stomach, and intestines. Visceral fat can also build up in the arteries and increase the risk of health problems. The best way to prevent excess visceral fat is to exercise on a regular basis.7


The connection between the two

Part of the reason for this confusing relationship is due to the fact that we use the exact same word to talk about two completely different things. Thus, we understand where the idea that fat makes you fat comes from, but in reality, the culprit is excess calories.

So what’s the take away from all this? We want you to understand that dietary fats are a vital component of good health. They are not only an energy source but an important factor for a number of biological functions, including growth and development.  

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  • [1]
  • [2]  “Dietary goals for the United States: statement of The American Medical Association to the SelectCommittee on Nutrition and Human Needs, United States Senate.” R I Med J. 1977 Dec;60(12):576-81. 
  • [3]
  • [4] Gillingham LG, Harris-Janz S, Jones PJ.“Dietary monounsaturated fatty acids are protective against metabolic syndrome and cardiovascular disease risk factors.” Lipids. 2011 Mar;46(3):209-28.
  • [5] Qian F, Korat AA, Malik V, Hu FB. “Metabolic Effects of Monounsaturated Fatty Acid-Enriched Diets Compared With Carbohydrate or Polyunsaturated Fatty Acid-Enriched Diets in Patients With Type 2 Diabetes: A Systematic Review and Meta-analysis of Randomized Controlled Trials.” Diabetes Care. 2016 Aug;39(8):1448-57.
  • [6] Simopoulos, Artemis P. "The importance of the ratio of omega-6/omega-3 essential fatty acids." Biomedicine & pharmacotherapy 56.8 (2002): 365-379.
  • [7] Dirk Vissers, Wendy Hens,Jan Taeymans, Jean-Pierre Baeyens, Jacques Poortmans, and Luc Van Gaal. “The Effect of Exercise on Visceral Adipose Tissue in Overweight Adults: A Systematic Review and Meta-Analysis” PLoS One. 2013; 8(2): e56415.


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