… Dieting through caloric restriction may temporarily reduce the size of fat cells, but does not decrease their number.

… Probably most overweight and obese people have a low metabolism which is partly or mostly responsible for their condition.

Dietary/calorie restriction not only creates the risk of nutritional deficiency, it can also slow the metabolism further. This is why dieters typically gain back their weigh plus more, following a crash program. And most diet plans are the short term, "quick loss" type.

What can you do? 
… Find out from a reputable professional if your metabolism is low. An oral temperature below 98.6 degrees F may indicate a sluggish metabolism. (See the article below.)

... Consider easy exercise as a healthy means of raising your metabolism and burning fat. More intense forms of exercise often will not do this long term.

… Be sure breakfast is part of a balanced diet. This can include some natural fats such as butter, vegetable oils and eggs.

… Learn as much as you can from reliable sources. Ask your nutrition-oriented doctor for recommendations.