Recently, we posted an infographic about a study that compared alternate day fasting vs daily caloric restriction (1).
The study found no difference in weight loss. Both diets were calorically matched.
Some people criticized the study. They argued that matching the diets for calories was a poor choice. Because, one of the benefits of a fasting diet is that you tend to eat fewer calories in total. By matching the diets for calories, this advantage would be taken away.
Indeed, different diets may result in a different caloric intake. Therefore, a study that matches diets in calories cannot investigate this effect.
So why would you ever do a study that is matched for calories?
By matching calories, the metabolic effects of two diets can be compared: does one of the diets make you burn more of the calories that are ingested.
Another infographic we posted was about a study that compared processed vs unprocessed foods (2). These diets were not matched on calories (subjects could eat as much as they wanted). The study showed that subjects ate more during the processed diet, and therefore gained more weight compared to the unprocessed diet.
Again, there were some people who criticized the study. Ironically, they argued that the diets should have been calorically matched to investigate the metabolic effects of the diets…
Take home message: there’s no perfect study. No study can provide all answers and make all relevant comparisons. The effect of a diet on caloric intake and metabolic effects are both important to know. A good study is a study that provides at least one useful piece of information.
Yes, i abdolutely agree. Intuitively we all know that some food components e. G fiber have a high satiating effect, if you want to investigate satity your study must not be calorically matched 😀
Yeah, this is what bothers me about intermittent fasting, keto, while foods, or just higher protien diets. We already know that calorie matching makes things the same, but people are way more intuitive than we give them credit for. If one is much more satiating or better at limiting calories without much effort, and the goal is to lose weight, gain muscle, and get healthy, why match them?