Many dieters believe that eating specific foods to boost metabolism can cause more weight loss. Some foods are thought to have properties that raise the metabolism, for instance, spicy foods like hot peppers, which make the body expend energy but do not contain many calories. Also often cited on lists of foods to boost metabolism are broccoli, grapefruit, and green tea, along with other similar foods.
A common attempt at choosing foods to boost metabolism includes compiling a list of "negative calorie" foods. These foods are known as negative calorie foods because some dieters believe they contain so few calories that the body actually has to use more energy to digest the foods than it actually absorbs from them, resulting in a net loss of calories. Typical examples of negative calorie foods include the aforementioned broccoli and grapefruit, as well as several others such as apples, oranges, and celery.
Many dieting and fitness enthusiasts are wary about supporting the idea of negative calorie foods. Too many variables, for example, individual body weight and personal energy expenditure, make it difficult to determine exactly how much energy that any one person will extract from a food. Many state that there is no such thing as a negative calorie food at all, and argue that the idea is propagated from hype instead of scientific evidence.
Some extreme fad diets, such as the grapefruit diet, claim that by narrowing your entire diet down to one food or food group, usually a "negative calorie" food, you can speed up your metabolism and reduce your caloric intake so drastically that you will drop multiple pounds of weight in just days. Many people do experience a dramatic loss in weight with diets like these, but it is usually just a loss of muscle and water weight, with very little fat loss. Nutritionists also often point out that dieters can make the mistake of lowering caloric intake too low, which can actually slow the metabolism instead of boosting it, regardless of what foods are eaten. Based on these principles, many nutritionists and diet experts suggest that, instead of eating only foods to boost metabolism, you should focus on consuming healthy, low calorie foods. Most or all of the metabolism boosting foods are very healthy and low calorie, and are often a good choice to eat as a snack or along with a meal.