These days, dietary fat is a hot topic in the news, with butter even making the cover of Time Magazine! This is no surprise. After over 50 years of dietary fat being vilified, research is coming to the forefront suggesting that fat is not the enemy it has been made out to be. In fact, the research leading to the widespread condemnation of fat has come into question as it appears that the lead researcher, Ansel Keyes, had a vested interested in his hypothesis being proved correct, and thus, the results of his studies were warped to make them appear stronger than they were, incorrectly stating that dietary fat leads to heart disease. 

We’re all familiar with the commonly stated “facts” on fat. 

  • If you eat fat, you’ll get fat
  • Fat causes heart disease
  • Fat raises cholesterol
  • Saturated fat clogs your arteries
  • Vegetable oils are the only healthy type of fat

You make think these claims are true, but the latest research demonstrates the contrary. The right fats, consumed in the right way, can help improve measures of health, including weight and blood sugar, which can significantly improve your diabetes.

Unfortunately, Ansel Keyes’s research resulted in decades of misinformation, and was incorporated into the building blocks of dietary recommendations set forth by prominent institutions like the American Heart Association and American Diabetes Association.  

Could a low-fat, high-carbohydrate diet actually be perpetuating a systematic condition of weight gain, elevated blood lipids and blood sugar?  Could people with blood sugar issues actually be better off consuming more fat and less carbohydrates and could such a diet actually prevent the onset of Type 2 diabetes altogether?

This is an area of extreme controversy. In answering these questions, it’s important to look at the research, deeply and critically. When it comes to research, the gold standard is the randomized controlled trial, and the size of the study matters. So while research continues to emerge, it is important to take into account the strength and size of the studies providing the results. Before getting into that, here is a brief synopsis of the types of dietary fats we’ll be talking about: We can’t just call fat into question as a macronutrient unto itself, as there are multiple types of fat.

  • Monounsaturated fat is found mostly in olive oil, olives, avocados, and macadamia nuts. It’s carbon chain contains only one double bond, making it a plant-based oil that is relatively stable, though not at very high heat. 
  • Polyunsaturated fats come in different forms – from vegetable oils to omega-3-rich fatty fish oils. “Poly” means many, and refers to multiple double bonds in the carbon chain of this fat molecule. The more double bonds present in a chain, the more opportunities the oil has to be oxidized (in the body – this looks like rust). For this reason, polyunsaturated fats are not particularly stable and can go rancid quickly. Omega-6 rich fatty acids, found in most vegetable oils like corn oil, have inflammatory properties. Specific omega-6 polyunsaturated fatty acids, however, found in evening primrose oil, borage oil, or black currant seed oil are anti-inflammatory in nature. Omega-3 fatty acids are anti-inflammatory polyunsaturated fats, famously found in fatty fish, but also in flaxseed, algae, and chia seed.
  • Saturated fats are solid at room temperature – like butter and coconut oil. These are those fats that have been long implicated in the development of heart disease. The carbon chains of these fats are saturated with hydrogens. This makes saturated fats a non-reactive chemical structure. Saturated fats are stable at high heats, not likely to oxidize or cause rusting in the body.
  • Trans fats are definitely the worst of the bunch and there is no argument here. They are a man-made solid fat, created with a chemical hydrogenation process leading to its long shelf-life. They are toxic to the human body and have been shown to lower good cholesterol and increase bad cholesterol. This fat truly does play a role in heart disease.

The type of fat we eat affects how it behaves in our body, and our overall diet plays a role. If we eat the right type of fat-rich diet, we can actually see improved measures of health, such as improved metabolism, blood sugar, weight, cholesterol, and even decreased appetite.

Some things to take into account when thinking about a lower carbohydrate, higher fat diet.

  • Sugar is actually what makes us fat, not fat. When we eat more sugar, our cells become insulin resistant. Our bodies produce more insulin – causing us to store fat – in order to try to get the unburned glucose out of our blood stream. Sugar and carbohydrates in combination, however, can cause a real problem (think bread and butter, macaroni and cheese, ice cream), so a high fat AND high carbohydrate diet will not be healthy and will lead to weight gain.
  • When we eat low-fat diets we tend to eat higher-sugar diets. The lower the fat, the hungrier the person, oftentimes. Not only that, but low-fat products are usually higher in sugar to account for the texture and mouthfeel lost when taking out the fat. We have been taught to think that low-fat diets lead to lower cholesterol and fewer heart attacks. But 75 percent of people who have gone to the emergency room due to a heart attack had normal cholesterol. They did, on the other hand, have type 2 diabetes or prediabetes.
  • A review of all published research on saturated fat in the American Journal of Clinical Nutrition found no correlation between heart disease and saturated fat. (1)
  • Quality matters!  Saturated fat in grass-fed butter will have a different effect than saturated fat in a burger from a factory farmed cow. This is also important to note when evaluating studies. In one study, people with prediabetes whose muscles do not efficiently uptake glucose slowed their progression to type 2 diabetes by replacing saturated fats with polyunsaturated fats. This was not, however, a randomized controlled trial, but researchers concluded that intake of polyunsaturated fats may benefit some types of prediabetes, but it is also important to take into account which polyunsaturated fats were tested in this study. Testing omega-3 fats compared to feed lot farmed bacon fat would likely yield different results that testing corn oil in place of extra-virgin coconut oil. A fat is not a fat is not a fat. (2)
  • Type matters! As mentioned trans fats are very inflammatory, and so are vegetable oils. These should not be a part of a heart-healthy diet. 
  • Almost all Americans are deficient in omega-3 fats and we would all benefit from increasing this anti-inflammatory fat in our diets. Food sources include cold-water, low mercury fatty fish such as sardines, salmon, and mackerel, omega-3 rich eggs, plant sources such as flaxseed and chia seed, and omega-3 supplements.
  • Our cell membranes are made of fat, so when we eat healthy fats, our cells become healthier. When our cell membranes are healthy, they are more efficient in insulin and blood sugar metabolism.
  • Some diabetic patients, under the care of their physicians, may find that a diet higher in fat can help them lower their blood sugar, cholesterol, and weight as long as their carbohydrate consumption is reduced. It is important to work with a doctor as medication requirements may need to be adjusted and more closely monitored. 
  • Without adequate fat, our brains can suffer. Our brains are composed of 60% fat and we need enough of the omega-3 fat DHA in order to have functional neural communication. Inadequate omega-3 fat is correlated with mood disorders such as bipolar disorder, schizophrenia, and the all-too-common anxiety and depression.
  • Your skin and tissues need good fats. If you don’t have them, you might find that your skin is dry, itchy, or flaking. Your nails may be too soft, or may be brittle and crack. Your earwax may be hard. You may find tiny bumps on the back of your torso or arms. Your joints may be stiff and ache.

Even with all of these potential benefits of a higher fat diet, studies still call dietary fat, namely saturated fat, consumption into question. 

More research from a study to be presented at the European Association for the Study of Diabetes showed that women with the highest consumption of fatty acids from fish, meat and other foods had a risk of diabetes 26% higher than those with the lowest intake. The study showed that some fatty acids had a greater risk than others and taking a critical eye to this work, it is important to acknowledge that fish, meat, and other foods contain very different fat subtype profiles. (3)  

Studies will likely continue to investigate the role of dietary fat on measures of health and progress has begun by the 2015-2020 Dietary Recommendation no longer advocating for decreased dietary cholesterol intake. The current recommendations include (4):

  • The avoidance of trans fat
  • Limiting saturated fat to < 10% of total daily calories
  • Replacing saturated fat with monounsaturated and polyunsaturated fats

Healthy fats to consider including are:

  • Avocados
  • Extra virgin coconut oil
  • Fatty fish like herring, mackerel, salmon, sardines
  • Grass fed meat and dairy
  • Nuts like almonds, macadamia nuts, pecans, and walnuts
  • Olives and olive oil
  • Seeds like chia, flax, hemp, pumpkin and sesame

By Nicole Anziani MS, RD, CDN, CDE, HHC, CPT
Cecelia Health Certified Diabetes Educator