I don't like putting clients on or recommending 'diets' to people. A diet assumes that you are going to change the way you are eating for a short period of time and then once you reach your goal you are going to go back to the way you were eating previously. The problem with a diet is that it isn't realistic.
The most common way to diet I see is very low calorie intake. A decreased amount of daily calories can lead to weight loss but it can also lead to malnutrition, a slower metabolism, reduced bone mass, fatigue, long-term changes in appetite gut hormones, regaining weight, and retention of fat. All of these are the body's response when it feels like it is starving and it isn't sure it is going to get more nutrition tomorrow.
The realistic approach to losing weight while looking at caloric intake is to make sure you are eating the proper kinds of foods that give you the best types of calories. Not all calories are the same and it's important to make sure you are getting them from nutrient dense foods.
Another way I see people dieting is through fad diets. Keto, paleo, Whole30, Atkins, Weight Watchers, The Zone, South Beach, Raw foods, Nutrisystem, Mediterranean, Volumetrics, Macrobiotic, Alkaline..etc. These are all "lose weight quick" plans. Most of these diets are designed with the idea that you need to see results quickly to stick with it. Some of them do that and some of them may take a little longer, but the problem with all of these is that they promote decreasing one of the macronutrients that your body needs.
"Lower the amount of carbohydrates" "Low carb diet" "High protein diet" "High fat diet" "Low fat diet"
The media in partnership with these different diets, does a great job of promoting one macronutrient and telling you that you need it the most. Your body needs all three macronutrients to survive and thrive.
Fat is an important fuel for your body. It helps your body when it needs more energy. Your organs convert fat for it's needs immediately and then stores the rest for later when there is too much. Fat also plays 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. When you reduce fat you are putting your brain function at risk, hormone imbalance, and you are keeping your body from fueling your body properly.
Carbohydrates are important for your brain and your nervous system. Healthy carbs come from fruits, vegetables, and whole grains. Your body uses carbs to make glucose and it uses glucose for immediate energy needs, like running. When you stop eating carbs you lose water weight, but when you start eating carbs again, like most will, then you gain all of that water weight back. That can be up to 10 lbs. I recommend eating the right kinds of carbs- fruits, veggies, and whole grains. Your body cannot go without carbs and it's important to nourish it properly with the right nutrients.
Protein has been labeled the king of all macronutrients. There is a lot of media around protein and how you need your body weight in protein. That can actually make you sick. You don't need your body weight in protein, you may only need a maximum of 43 grams if you're a woman or 62 grams if you are a man. When you eat protein your digestive system breaks down the protein and delivers the separated amino acids to the body's cells.
Now the body takes those amino acids and uses them to make proteins either for itself or the circulatory system. So, why do you need protein? You need it to supply the amino acids from which the body can make its own proteins- it's a building material. The body will make it's own proteins to repair cells, build tissue, regulate enzymes/hormones/antibodies/fluid balance/transportation, and energy. It's important to get protein from nutrient dense sources and not get too much so that you aren't overloading your system.
The point is that you need all three macronutrients in the right amount. Decreasing one may make you lose weight but it throws off your whole body. You don't want to malnourish your body just to lose weight. You want to look at the nutrients you are eating and measure the value of the calories in those nutrients.
When you start to value the nutrients in foods and what they provide you then you are changing your lifestyle and getting yourself on a path to lead a healthier life that may lead to the proper weight for your body. Look for plant based options, foods with natural high fiber, foods rich in antioxidants, and foods that promote anti-inflammation.