Measuring calories burnt and calories consumed is trickier than it looks reading nutriction facts and calories/hour tables.

Also, your body is much smarter than you in adapting to changes to calories getting in and out. If you accept that human body do a lot more to influence your behavior than your consciousness realize, you have to admit that not all things depends solely on one's will. Calories consumption are one of those things.

Also, you can study large groups of people for macro influences of a diet at humand body. But individually is known to provide a lot of diversity. Two people on the exactly same diet and exercise routine won't have the exactly same body effects. Much of that was put in the account of DNA. But maybe some of this is due to gut bacteria. That's a possibility worth researching.