Choose healthy sources of fat, such as nuts, seeds, oils and fatty fish, to maximize nutrient intake when adding more fat to your diet. Image Credit: sergeyryzhov/iStock/GettyImages

High-fat diets are becoming more and more popular. From athletes and bodybuilders to nutritionists, everyone is saying that you must eat fat to burn fat. This nutrient fills you up quickly, curbs hunger and boosts your metabolism. But is it really healthy to load up on fats — and what can you expect in terms of weight loss?

The Role of Dietary Fat

Most dieters avoid fat at all costs. They always choose low-fat dairy, cook with little or no oil, and would never touch butter, walnuts, ghee and other high-fat foods. While it's true that eating too much fat can affect your health and well-being, you still need this nutrient to function optimally.

As the American Heart Association points out, dietary fats are essential for health and well-being. They promote cell growth, keep your body warm and supply energy. These nutrients also assist in hormone production and protect your vital organs.

However, not all fats are created equal. Monounsaturated and polyunsaturated fats are considered healthy. Saturated fats can be beneficial when consumed in moderation. Trans fats increase bad cholesterol, reduce good cholesterol, trigger inflammation and clog your arteries. In the long run, they may contribute to heart disease, insulin resistance, diabetes, stroke and other life-threatening diseases.

Read more: 18 Fat-Rich Foods That Are Good for You

Dietary Fat Fuels Your Body

In order to understand the role of fat in weight loss, it's important that you know why your body needs it in the first place. Dietary fat serves as a source of energy. Each gram provides nine calories. Carbs and protein, by comparison, deliver four calories per gram.

High-fat foods, such as avocado, tuna, salmon and olive oil, are more nutrient-dense than high-protein and high-carb foods. That's why you feel full faster after eating peanut butter or walnuts rather than chips or cookies. If you go on a low-carb diet, your body will use fat for fuel.

Read more: Advantages & Disadvantages of Fats

The ketogenic diet, for example, is high in fat and low in carbs. This eating plan shifts your metabolism from burning glucose to burning stored fat for energy. According to Harvard Medical School, ketogenic diets exhibit neuroprotective effects and support weight loss. Over time, they may improve glycemic control and blood lipids.

Eat Fat to Burn Fat

A diet rich in healthy fats can help you slim down in more than one way. First of all, these nutrients promote satiety, making it easier to reduce your daily food intake. A 2017 clinical trial published in the journal Nutrition found that diets high in polyunsaturated fatty acids (PUFAs) caused positive changes in fasting and postprandial physiological markers of satiety and hunger in as little as seven days.

Another study, which appeared in the FASEB Journal in 2017, investigated the effects of avocado consumption on appetite control. This fruit is rich in both fiber and dietary fats. According to researchers, increasing the fat and fiber content of a meal promotes satiety to a greater extent then a low-fat, high-carb meal. Subjects who ate avocado for breakfast experienced less hunger and consumed less food over the next six hours.

Read more: How Many Grams of Fat Should You Eat Per Day?

Health experts say that it's time to end our fear of fat. A 2016 randomized controlled trial featured in The Lancet Diabetes & Endocrinology shows clearly that high-fat Mediterranean-style diets lead to a greater reduction in body weight and abdominal obesity compared to traditional diets. Dieters who embraced this eating pattern lost massive weight without restricting calories or engaging in regular exercise. Their body weight was monitored closely for five years.

Does the Keto Diet Work?

An example of a high-fat diet for weight loss is the keto diet. This eating plan enjoys huge popularity in the fitness and bodybuilding community. According to the Center for Nutrition Studies, the ketogenic diet was developed in 1924 as an alternative treatment for epilepsy in children. Researchers found that limiting protein and carbs while increasing fat intake caused an increase in ketone bodies, leading to a metabolic state known as ketosis.

Under normal circumstances, your body uses carbs for fuel. After ingestion, carbs are converted to glucose and used for energy. The excess is converted to glycogen and stored in the liver and muscles for later use. Fasting, high-intensity training and low-carb diets deplete the body's glycogen stores, so the liver begins producing ketone bodies for energy.

The ketogenic diet is based on the principle that eating fat burns fat. If you cut back on carbs for a longer time, ketone bodies start to build up in the blood. Your body enters ketosis and begins to use fat to sustain itself. These metabolic changes, though, cause unpleasant symptoms like bad breath, frequent urination, fatigue, weakness and the so-called keto flu. However, dieters start to feel better as soon as they enter ketosis, which may take a few days to a few weeks.

Potential Benefits of Ketogenic Diets

The benefits of a high-fat diet for weight loss are supported by science. According to a 2014 review published in the International Journal of Environmental Research and Public Health, ketogenic diet plans suppress hunger and trigger positive changes in ghrelin, leptin and other hormones that influence appetite. Furthermore, they increase fat burning and reduce fat storage, boost metabolic rate and stimulate thermogenesis due to the thermic effect of protein.

Some of the studies cited in the review indicate that ketogenic diets may improve mood, prevent cognitive impairment and reduce insulin resistance. In clinical trials, mice fed with low-carb, high-fat foods lived longer and had a lower risk of cancer and metabolic syndrome.

A more recent article, which was published in the Journal of Postgraduate Medicine in 2017, points out that ketogenic diets may be effective in the prevention and treatment of diabetes, polycystic ovary syndrome, depression, metabolic and endocrine disorders, Alzheimer's disease, migraines, epilepsy and more.

Researchers agree that despite its health benefits, the keto diet isn't safe for everyone. Its potential side effects, which range from metabolic acidosis to anorexia, cardiomyopathy and severe hepatic steatosis, shouldn't be overlooked.

Dietary Fat: Friend or Foe?

A growing body of research shows that dietary fats promote weight loss and support overall health. The problem, though, is that many diet plans, including the keto diet, don't restrict calories or the types of fats consumed. Some even suggest meal ideas like eggs and bacon, buttery meats, fat bombs and pork rinds. These foods are high in saturated fats and processed ingredients that may lead to chronic health problems.

If you only focus on macronutrients, you could be missing out on essential vitamins, minerals, antioxidants and more. Plus, you might not get enough fiber in your diet, which can lead to constipation and gut flora imbalances.

Read more: 9 Delicious Recipes Made With Healthy Fats