Whenever you go grocery shopping, its inevitable that you will find food products advertising being ”LOW FAT”. Companies often advertise their products in this way because it is a common conception that eating fat makes you fat. By doing this, they are able to attract consumers that are trying to lose weight. However, is it actually true that dietary fat is ”unhealthy” and should be avoided for weight loss?
A well controlled study published in 2009 analyzed the health effects of diets which focused on different macronutrients. In this study, they compared high-fat diet to a low-fat diet. Participants of the study had their resting metabolic rate and energy expenditure measured. Every dieting participant was given a diet representing a deficit of 750 kcal. After following the diet for two years, it was shown that both groups of participants lost weight, with no significant difference in weight loss between the high-fat and low-fat groups (3.9 and 4.1 kg, respectively; P=0.76). 
The study not only showed that a high fat diet is as optimal as a low fat diet for losing weight, but also showed that it had other health benefits. After two years, all the diets reduced risk factors for cardiovascular disease and diabetes. It was shown that all the diets increased HDL cholesterol levels, decreased triglyceride levels, and decreased blood pressure. In this regard, there were some differences in effects that were dependent on variance in macronutrient composition. However, we can determine that as long as a caloric deficit is maintained, health benefits will be evident on either high-fat or low-fat diets.
So far, we have seen that high-fat diets are not detrimental to either health or weight loss and yield little difference to low-fat diets in those aspects. There are, however, advantages of pursuing a moderate to high fat diet over a low fat diet. Studies in men have shown that eating a high-fat diet results in increased free testosterone and total testosterone levels . Alternatively, reducing the amount of fat in your diet, while keeping your caloric intake constant has shown to decrease free testosterone and total testosterone levels [3,4]. Therefore, eating a diet higher in fat content can be advantageous in both a cut or bulk, as testosterone confers the ability to help protect against catabolism of muscle and increase muscle mass.
Dietary fat also provides fat-soluble vitamins like A, D, E, and K. I therefore believe that it was preferable to have atleast 20% of your total energy intake from fat. In conclusion, fat in your diet should not be avoided, but instead, eaten in moderation.
Afterthoughts: It should be noted that fat intake should be from a variety of sources and that the only fats that you should completely avoid are artificial trans-fats. 
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