WHAT WE KNOW ABOUT DIETS

Most popular diets have to do with weight loss, when they really should be concerned with body fat loss in those who are overfat. When evaluating such diets we should give consideration to the following points:

Whether there are any other advantages in the dietary change, such as reduced risk of:

essential nutrient deficiency;
various chronic diseases, such as osteoporosis (thinning of bones), macrovascular disease ('hardening of the arteries' or atherosclerosis), certain cancers, diabetes of the non insulin dependent types and more;
developing a weight disorder or, more correctly, a disorder of body composition including fat.

The composition of our body. A body consists of fat, lean mass (muscle, organs), bone and water. Weight may change when any of these change. Rapid weight change is more likely to be a fluid shift, than a fat change. Many diets promoted exploit the fact that when there is marked reduction in energy (kilojoule) intake, there is a loss of carbohydrate stores (glycogen) in muscle and liver, and with it water. Thus, loss of water may account for loss of weight in these cases. The same applies to going on to a low carbohydrate from a high carbohydrate diet. But the longer the weight loss goes on or is maintained, the more likely it is to be of fat. Some muscle is usually lost with reduced energy intake as well. The corollary to these observations is that when usual or preferred energy or carbohydrate intakes are resumed, water is regained and is reflected in a weight increase.

Check body fat by pinching up a fold of skin with thumb and forefinger (more than 1 inch or 25 mm on the abdomen is too much) or measurement of abdominal girth or both.
The distribution of body fat is important. That around the abdomen and trunk is more of a health risk than that at the hips.
Maintenance of preferred body composition overall is best achieved by regular physical activity, at least 3 to 4 times per week for 20 or more minutes at a time, or something that produces a light sweat. Or, walking 30 to 60 minutes every or every other day. Climbing stairs is one of the best exercises! And don't forget skipping if you can manage it!
Eat a wide variety of foods, and ensure that they are low in fat, especially animal or saturated fat, and minimise alcohol intake. Fat and alcohol are the most 'energy dense' macro nutrients (macronutrients include protein, carbohydrates, alcohol, fat and dietary fibre).