There are various types of diet eg. IIFYM diet, vegan diet, chocolate diet, etc. A healthy diet is a diet that helps to maintain or improve overall health.
Dieting is the only game where you win when you lose! 😉
A healthy diet provides the body with essential nutrition: fluid, macronutrients, micronutrients, and adequate calories. Good nutrition is an important part of leading a fit lifestyle. Combined with physical activity, your diet can help you to reach and maintain a fit body composition, reduce your risk of chronic diseases (like heart disease and cancer), and promote your overall health.
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A fad diet is a diet that is popular for a time, similar to fads in fashion. Fad diets usually promise rapid weight loss or other health advantages, such as longer life. They are often promoted as requiring little effort and producing a "quick fix". In many cases, the diet is characterized by highly restrictive or unusual food choices, which can cause serious health problems.
IIFYM, or “If It Fits Your Macros,” is a type of flexible dieting that helps people lose weight without feeling overly restricted. Rather than focusing on calories, This diet tracks macronutrients instead — namely protein, fat and carbohydrates. This allows for much more flexibility since all foods can be enjoyed as long as they fit into your macros for the day.
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The major upside of this diet is that it emphasizes the idea that all three macronutrients—fat, carbs, and protein—are important, and doesn't make any food off-limits.
Since you can eat anything and everything in this type of diet you lack of micronutrients. The macros of this diet are high protein, high carbohydrates, low fat diet. Due to the high amount of carbohydrates your blood glucose levels are going to be high that produces higher amounts of Insulin in the body and all glucose will stored in adipose tissue (fat cell). These spikes of Insulin lead to diseases like type 2 diabetes, obesity, PCOS, thyroid and blood pressure.
The approach of counting macronutrients over calories is a better option because the principle of thermodynamics, which is calories in calories out is irrelevant to our body. Not all calories are same.
Interested in following this diet check out their Macro Calculator