Fats are an essential nutrient and one of the primary energy sources for the body. They also play a big role in weight management, absorbing nutrients, maintaining healthy skin and hair, regulating body temperature, supporting immune function, insulating internal organs, and hormonal balance. You can see right off the bat why there are just so many low-fat diet risks to be aware of!
While a balanced diet that includes plenty of plant foods, like vegetables and some fruit, is key for long-term health, fats are actually needed to properly absorb the fat-soluble vitamins found in many plants — including vitamin A, D, E and K. Fats also make us feel satisfied after eating — which is not just a nice perk that should be overlooked.
Most healthy sources of fat are also ultimate fat-burning foods. Their ability to make our food taste good, turn off hunger and stop overeating has a lot to do with weight management.
Why We Need Fats: The Low-Fat Diet Risks That May Surprise You
Fats in general have gotten a bad rap in our heart-healthy and fat-obsessed diet culture. For decades, we’ve been told to put fatty foods like coconuts, eggs, fatty cuts of meat and full-fat dairy in the “foods to avoid” category. Since the government’s 1980 Dietary Guidelines were established over 30 years ago, dietary policy has focused on reducing total fat in the American diet to no more than 30 percent of a person’s daily calories. And many of the most popular “diet plans” over the years have reduced fat to much lower levels than this.
Although we hear much more about healthy fats in the mainstream media today, anything high-fat (such as in the keto diet) still sets off alarm bells for most of us and raises concerns about packing on the pounds. Low-fat, diet and light products of all sorts continue to pack grocery store shelves — but what are the real risks of consuming these foods over the full-fat varieties?
Not all fats are created equally and not all affect the body in the same way. While processed and refined fats found in boxed foods and most restaurant fare can be harmful, other types of natural fats have beneficial, life-extending properties. When we miss out on fats in our diets, we can quickly find ourselves feeling tired, moody, constantly hungry, unable to kick cravings and resentful over our restrictive diets.
Some of the biggest arguments for including more fat in your diet boil down to fat’s ability to help control hormones, especially insulin. Low-fat diet risks include hormone imbalances and insulin resistance commonly linked to diabetes, weight gain, gut problems, cognitive disorders and more.
As famous fat advocate, doctor and author David Perlmutter, MD, puts it in his book “Brain Maker,”
For the greater part of the past 2.6 million years, our ancestors’ diets consisted of wild animals and seasonal fruits and vegetables. Today most people’s diets are centered on grains and carbs — many of which contain gut-blasting, microbiome-damaging gluten whose downstream effects reach the brain. Even setting aside the gluten factor, one of the main reasons that consuming too many grains and carbs is so harmful is that they spike blood sugar in ways other foods, such as fats, meat, fish, poultry, and vegetables, do not.
Basically, you can think of it this way: In place of fat, most people eat more carbohydrates. This also includes high-carb foods with plenty of sugar. Carbohydrates, including whole grains, have been positioned as the foundation of a healthy diet for decades (does 11 recommended daily servings of bread, cereal, rice and pasta ring a bell?), but in reality, they’re highly overconsumed today, contributing to a host of diseases.
7 Risks of Low-Fat Diets
1. Poor Brain Function
The brain is largely made up of fat and requires a steady stream of fatty acids to perform optimally. There seems to especially be a special protective factor when it comes to cholesterol and the brain. Cholesterol has an important role as a critical brain nutrient, essential to the function of neurons and neurotransmitters, so despite what most people think, low cholesterol levels can be worse than high. The brain basically requires a high amount of cholesterol as a source of fuel or energy, but since brain neurons themselves cannot generate significant amounts of cholesterol on their own, we must get our required cholesterol from our diets to feel our best and remain “sharp.”
Research shows that people who have the highest cholesterol level intakes usually perform better on cognitive tests than those with lower levels. According to results from the benchmark 2005 Framingham study, “lower naturally occurring total cholesterol levels are associated with poor performance on cognitive measures including abstract reasoning, attention/concentration, word fluency, and executive functioning.”
This means that a major low-fat diet risk includes poor job performance, low energy, changes in your mood, “brain fog” and so on. This is why some of the best brain foods to boost focus and memory actually have high levels of healthy fats.
2. Compromised Heart Health
While we’ve been led to believe the opposite for many years, research continues to confirm that heart disease (including coronary artery disease, the leading cause of heart attacks) likely has much more do with inflammation — which is at the root of most diseases — than from high fat or cholesterol intake. This means that an inflammatory diet including lots of sugar, refined carbs, low-quality proteins and processed vegetable oils is actually more threatening to your heart that a diet high in fat — even saturated fat. It’s much more beneficial for your heart to eat anti-inflammatory foods that contain healthy fats.
Beneficial effects of monounsaturated fats on heart health are especially supported by clinical studies. Consumption of dietary MUFAs promotes healthy blood lipid profiles, lowers cholesterol levels naturally, mediates blood pressure, improves insulin sensitivity and regulates glucose levels
Think about it this way: The glorified Mediterranean-style diet that is high in fats from extra-virgin olive oil, nuts and fish exceeds over 40 percent of calories coming from fat. This is well above the government’s recommendation to keep fat intake between 20 percent to 30 percent of total calories. And yes the Mediterranean diet has been shown to significantly reduce cardiovascular disease, diabetes and long-term weight gain.
But what about saturated fat intake and heart disease? Here’s the truth about saturated fat: If you’re worried about saturated fat causing heart attacks, strokes and heart disease, know that evidence that saturated fat leads to heart disease is weak at best.
Some studies do show that increased saturated-fat intake can raise cholesterol levels, but there hasn’t been a strong relationship between cholesterol levels and heart disease proven. Some studies on low-carbohydrate diets, which usually have higher levels of saturated fats actually, suggest that they don’t raise blood cholesterol and can even be beneficial on cardiovascular disease risk markers like triglyceride levels.
3. Hormone Imbalances (Including Sex Hormones Testosterone and Estrogen)
Eating enough fats is one of the most important things you can do to balance hormones naturally. Cholesterol and other fats play a fundamental part in building cellular membranes and hormones. Certain kinds of fats, including cholesterol, also act like antioxidants and precursors to some important brain-supporting molecules and neurotransmitters. These include vitamin D (which actually acts more like a hormone in the body more so than a vitamin) along with other hormones like testosterone and estrogen.
One scary low-fat diet risk is an increased risk for infertility and other hormonal issues in women. Some studies have found that low-fat diets raise the risk of menstrual problems and difficulty getting pregnant. For example, a 2007 study conducted by the Department of Nutrition and Harvard School of Public Health found that high intake of low-fat dairy foods may increase the risk of infertility whereas intake of high-fat dairy foods may decrease this risk.
4. Weight Gain and Overeating
Look at any of the recent research involving weight gain (or loss) and fat intake, and you’ll quickly realize the established relationship between fat intake, your hormones and weight fluctuations. We know that many people who go on “diets” tend to gain back all of the weight shortly after. Why does this happen?
One explanation is that weight loss elicits biological adaptations that result in a decline in energy expenditure (adaptive thermogenesis) and an increase in hunger, both of which promote weight regain. But certain studies have found that a higher-fat diet with lower carbs can help prevent this from happening. On top on that, most people find that diets higher in fat are more satiating and turn off hunger signals and appetite much more so than lower-fat diets do. This is because fats turn on your fat-burning switch by impacting ghrelin hormone levels.
One study published in the Journal of the American Medical Association in 2012 examined the effects of three popular diets on a group of overweight or obese young adults. The study’s participants tried each of the different diets for a one-month period so researchers could compare the effects.
The three diets provided the same number of calories but differed in proportions of fat, protein and carbohydrates. The “low-fat diet” had 60 percent of total calories coming from carbohydrates, 20 percent from fat and 20 percent from protein. The “low-glycemic diet” had 40 percent of the calories coming from carbohydrates, 40 percent from fat and 20 percent from protein. Finally, the third “low-carb diet” had just 10 percent of the calories coming from carbohydrates, 60 percent from fat and 30 percent from protein.
Make no mistake about it, the low-carb diet featured a lot more fat than a person eating the Standard American Diet is used to. In fact, the average American probably eats something similar to the “low-fat diet” ratio that is highest in carbs.
What were the results after comparing the three diets? Those on the low-carb, high-fat diet burned the most calories and also improved their insulin sensitivity best during the four-week period. Measures of resting energy expenditure (REE) and total energy expenditure (TEE), which really means the amount of calories someone burns each day, were the lowest in the low-fat diet group, intermediate with the low–glycemic index group and the highest in the low-carbohydrate group.
According to the researchers, they believe that
Diets that aim to attenuate (lower) the increase in blood glucose levels after eating—specifically low–glycemic index (emphasizing carbohydrate source) and very low-carbohydrate (focusing on carbohydrate restriction) diets — have been hypothesized to have metabolic advantages. Reducing dietary glycemic load may elicit hormonal changes that improve the availability of metabolic fuels and thereby decrease hunger and voluntary food intake.
5. Higher Risk of Insulin Resistance and Diabetes
Clinical studies have shown us that excess weight gain and insulin (or blood sugar control) are highly connected, but we know that eating plenty of healthy fats is one of the keys to controlling insulin. Insulin is sometimes called our “fat-storing hormone.” It helps usher glucose into our cells, which lowers our blood sugar levels after a carbohydrate or sugar-containing meal.
It appears that different types of fat have different effects on insulin action. Given the importance of insulin resistance in the development of diabetes and heart disease, establishing appropriate levels of fat in the diet is an important clinical goal for lowering the “diabesity” epidemic. Studies that have examined the effects of various diets with different levels of fat are revealing in telling us that lower-fat, higher-carb diets might pose a higher risk for insulin resistance (and weight gain), although there’s still some debate as to what types of fats should be most emphasized as natural diabetes cures.
Epidemiological evidence and intervention studies clearly show that monounsaturated and polyunsaturated fatty acids improve insulin sensitivity through modifications in the composition of cell membranes. Substituting saturated fat with unsaturated fat seems to have beneficial effects on insulin sensitivity, although the clinical significance of fat quality alone is still unclear. Either way, we know that diets that are higher in fat tend to be lower in carbohydrates and sugar, which is beneficial for diabetes prevention.
There’s also some evidence that suggests that insulin resistance status may affect adherence to weight loss diets. It’s possible that people with existing insulin resistance might be more likely to give up a healthy diet and therefore experience less weight loss success. This seems to be especially true for people following low-fat diets — research shows diminished weight loss success in insulin-resistant women assigned to a low-fat diets compared to those assigned to a low-carbohydrate diets.
6. Higher Risk for Depression and Anxiety
Fatty acids play an important role in higher brain functions that control moods, so eating enough healthy fat sources is one key to following an anti-depression diet. Some neurotransmitters, such as endocannabinoids, are synthesized from fatty acids, suggesting that fatty acid metabolites derived from dietary fat can affect the central nervous system.
While it appears that trans-fat intake can raise depression risk, studies have found an inverse associations between consuming MUFA, PUFA and olive oil fats and depression risk. In other words, higher-fat diets might lower depression and other mental disorder risks. Research has shown, for example, that supplemental PUFAs and specifically omega-3 fatty acids in the diet cause significant improvement in depressive symptoms in humans. In fact, it’s now believed that use of omega-3 PUFA supplements is effective in treating patients with diagnosis of major depressive disorder.
7. Gut-Related Problems
Higher-fat, high-fiber diets are now correlated with a healthier gut environment, or microbiome. A diet with plenty of naturally occurring fatty acids and nutrients supplies the building blocks needed to nourish not only a healthy gut, but also a healthy brain, both of which are very connected — also known as the brain/body connection.
A diet that keeps blood sugar balanced keeps gut bacteria balanced, too. So this means that eating plenty of high-fiber plant foods (especially all vegetables) along with healthy fats feeds the good gut bacteria in the gut and produces the right balance needed to lower inflammation. One of the benefits of coconut oil is it can be especially protective over gut health and very easy to digest even for those with chronic digestive issues.
Avoiding Low-Fat Diets: The Fats You Need and Why
In February 2015, the U.S. Dietary Guidelines Advisory Committee finally changed its recommendation in regard to fat intake for the first time in 35 years! It sent recommendations to the government without any upper limit on total fat intake. It additionally declared that it does not recommended low-fat foods or diets for obesity prevention. This is a huge step in the right direction!
The main fats we must obtain from our diet include:
- Saturated fats (long- and medium-chain)
- Monounsaturated fats
- Polyunsaturated fats (especially omega-3s and some omega-6s)
These all have different effects on the body, and sometimes this can seem confusing. Ideally, saturated fats, certain polyunsaturated fats and monounsaturated fats should form the bulk of your fat intake. The polyunsaturated fats called omega-3 fatty acids (EPA and DHA) and the omega-6 fats called arachidonic acid should be consumed regularly. However, omega-6 linoleic acid should be consumed only in whole-food form from things like nuts, seeds and beneficial avocados instead of from refined vegetable oils (like sunflower, canola, corn, safflower oil).
How much fat do you need exactly? It’s not necessary to count macronutrients and obsess over number of grams, but this might be helpful: Choose a rough target for carbohydrate intake based on your individual needs, and assume your remaining calories will come from a combination of proteins plus fats. This ratio can definitely range depending on your level of activity, age and medical conditions, but for the average person, I recommend getting about 40 percent of calories from all carbohydrates combined, 30 percent from protein and 30 percent from healthy fats.
This might be more fat than you’re accustomed to eating, especially if you’ve been following what the government recommends, which is basically a low-fat, high-carbohydrate diet. On a higher-fat diet, you’re most likely to feel fuller between meals, have less carbohydrate and sugar cravings, think more clearly, and experience more energy — which is why you might be surprised to know there are benefits of butter, full-fat raw dairy products and dark meats. But remember that the quality of fat you eat is just as important as the quantity when it comes to your health!
Here’s a bit more about how each type of fat helps support you:
- Play an important role in bone health since they help absorb calcium into the skeletal system
- Protect the liver from damage, including from toxins like alcohol, prescription medications and chemicals found in household supplies
- Have beneficial effects on cardiovascular function, including reducing levels of lipoproteins and inflammatory substances that promote heart disease
- Improve lipid profiles by increasing HDL cholesterol, which is usually called the “good” kind
- Decrease triglycerides and make LDL (sometimes called “bad” cholesterol) particles larger and less risky
- Conjugated linoleic acid (CLA) also helps burn fat, which is found in grass-fed beef, beneficial raw dairy and certain other animal products
Medium-chain saturated fats (and medium-chain triglycerides) are especially beneficial. These are found in coconut oil, nutritious coconut milk, flesh, oil, butter and even naturally in human breast milk. They possess unusual properties that make them ideal for being easily metabolized and used for energy. But these are just some of the top health benefits of coconut oil and other MCTS; they also don’t require bile acids for digestion, and they pass directly to the liver to be used for bodily fuel. In addition to being a good energy source, they:
- Have antibacterial, antiviral and antioxidant properties found in lauric acid
- Can help repair the gut and reduce leaky gut syndrome, candida virus symptoms and other forms of inflammation
- Promote weight loss since they increase calorie expenditure and the temperature within the body (called thermogenesis)
- Help make you full and satisfied — especially since they taste great!
- Have a high smoke point so they’re perfect for cooking, even at higher heats
Monounsaturated fats possess beneficial oleic acid and are found primarily in olives or olive oil, avocados, some animal products (like eggs or lard), and certain nuts like macadamias and nutritious almonds. Even the American Heart Association and other governing bodies encourage MUFAs in the diet! Similarly to saturated fats, they help form the core structural fats of the body and are nontoxic. Monounsaturated fats are known for:
- Benefitting the heart and reducing cardiovascular-disease risk markers
- Reducing LDL cholesterol and triglycerides and increasing HDL
- Decreasing oxidized LDL cholesterol, reducing general oxidation (or free radical damage) and lowering inflammation
- Lowering blood pressure
- Decreasing the formation of blood clots
These are usually divided into two main categories: omega-6s and omega-3s. Omega-3 fats’ benefits come from eating wild-caught seafood like salmon, some meats and high-quality eggs, and in lower levels in nuts, seeds, green leafy veggies and sea vegetables. Omega-6 fats are found primarily in nuts, seeds and vegetable oils.
Most people get enough omega-6s from eating packaged foods, which contain low-quality vegetable oils, but are lacking in omega-3s foods; this can create its own set of problems, which is why obtaining omega-3s should be a priority for everyone.
Polyunsaturated fats (especially omega-3s):
- Have a number of anti-inflammatory effects
- Play a structural role in the body’s cells and brain
- Form cell membranes, regulate gene expression and aid in cellular function
- Help prevent depression and anxiety
- Support cognitive function and help prevent age-related cognitive decline
Read Next: The 5 Best Healthy Fats for Your Body
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