Though creating a calorie deficit by burning more energy than you take in is the most important factor when it comes to weight loss, it’s not the only thing that matters.

Relying solely on calorie intake doesn’t account for the large number of variables that may prevent someone from losing weight, even when on a very low calorie diet.

For example, hormonal imbalances, health conditions like hypothyroidism, metabolic adaptations, the use of certain medications, and genetics are just some of the factors that may make weight loss harder for some people, even when they’re on a strict diet.

This concept also fails to emphasize the importance of sustainability and diet quality for weight loss. Those following the “calories in, calories out” method typically concentrate solely on the calorie value of foods, not their nutrient value.

This can lead to choosing low calorie, nutrient-poor foods like rice cakes and egg whites over higher calorie, nutrient-dense foods like avocados and whole eggs, which isn’t the best for overall health.

Though this antiquated and incorrect theory is slowly being put to rest, many people still fear high fat foods and follow low fat diets in the hopes that cutting their fat intake will benefit their overall health.

Dietary fat is essential for optimal health. Plus, low fat diets have been linked to a greater risk of health issues, including metabolic syndrome, and may lead to an increase in insulin resistance and triglyceride levels, which are known risk factors for heart disease.

What’s more, diets that are higher in fat have been proven just as effective — or even more so — than low fat diets when it comes to encouraging weight loss.

Of course, extremes in either direction, whether it be a very low fat or very high fat diet, may harm your health, especially when diet quality is poor.