 What are some dietary strategies for the prevention and treatment of obesity? Large portion sizes are often targeted, and so restriction of portion size is an important element of many diet programs. But it's hard to get people to eat less food. A more effective approach may be to shift the emphasis from the quantity of food eaten to the quality of food eaten. By choosing foods with low calorie density, we can eat the same amount of food or even more food while losing weight. Are there foods with negative calories, foods that take more energy to digest than they provide? Does eating celery, for example, result in negative energy balance? Celery is a readily available whole food that has the ability to add bulk and flavor to a meal without adding excess calories. It's also subject to a renowned health myth that when consuming celery, there is a negative intake of calories and therefore the energy required for its digestion, assimilation, and nutrient storage is assumed to be greater than the energy it itself contains. So they put it to the test. A cup of celery by two stalks has 16 calories. To digest that much celery, it takes 14 calories. So no, the consumption of celery does not induce a negative energy balance, but you are only left with two calories. This fact, combined with the high fiber and water content of celery, does make it a good snack for inclusion in a diet for weight loss or management. Maybe negative calorie foods is not a myth after all, though. Researchers at Penn State offered people a meal of pasta, in which they could eat as much as they wanted. This is how many calories of pasta they ate. If in addition to the all-you-can-eat pasta meal, they gave people a small salad, what do you think happened? Did those 50 extra calories of salad just end up on top of the pasta calories? No. They ended up eating less pasta overall, and not just 50 calories less pasta, 65 less calories. And by adding a bigger salad, ended up eating 100 fewer calories. So effectively, the salad provided quote-unquote negative calories, right? They ate a salad on top of what else they were eating, ate more food, and ended up with less calories in their system, because it bulked up their stomach so much. Of course, it depends what kind of salad they're not talking about your typical commercially available salads with ranch dressing and cheese, right? You add those kinds of salads, and yeah, you do end up eating less pasta, but there are so many calories in conventional salads, you end up worse off calorie-wise in the end, but healthy salads worked. They conclude, eat less is not always the best advice for foods very low in energy density, such as water-rich vegetables like salad. Larger portions increase satiety, the feeling of fullness, and reduce meal calorie intake.