As a new dietitian, I welcomed patients asking for precise direction on what to eat. A patient who really wants to know exactly what to eat...what more could I want? I thought that if only I can tell someone exactly what to eat, then they would meet their health goals. Those who wanted to follow directions--awesome! At this point, I can't believe I once thought that!
Most of my patients have been through years or decades of trying to follow all sorts of diet instructions. Whether it was a diet plan from a wellness provider, a plan from a book, a diet program, a diet app.... they have followed it all. And often they followed these diets with great fidelity!
Some people will stay on these diets for days or weeks. Some can impressively stay on these diets for months. Many people will lose weight while they are on the diet. But the diet does not last. Eventually it gets impossible. And not for lack of willpower or self control. These are people who have jobs, take care of their families, keep up with school work, or do all sorts of other impressive tasks, so I can't attribute the end of their diet to lack of willpower or self control.
There are two main factors that together lead to the end of a diet: One, the diet, and two, human physiology. The diet is not a way humans are meant to eat, and our human physiology in that many people with obesity have a stronger hormonally-mediated drive to eat than people without obesity. I'll illustrate this in a way you may be able to relate.
Let's say you were on a water drinking plan. On this plan, you were allowed to drink 6oz every hour. It likely will be OK in the beginning. It might be a bit uncomfortable certain times of they day--maybe you wake up very thirsty, and you prefer to drink 2 cups of water right when you wake up. But you can basically tolerate it. Now, let's say it is a hot July day, and you are walking for 2 hours in the 95 degree heat. You have your water bottle in your backpack for your hourly 6oz drinking increments. You're faithfully trying to follow your water drinking plan, but the drive to drink is getting stronger and stronger. Eventually you cave in and drink a whole ton of water.
Most people can understand this drive to drink as a physiological drive. No one would really expect someone to just have "willpower and self control" and not drink. The drive to eat, even when not actually hungry, is still often a physiological drive--mediated by different hormones than the drive to drink, but a drive nonetheless.
Just like you can, to some extent, delay a drink when you are thirsty, a person on a diet can also, to some extent, ignore the drive to eat. That is why diets last for weeks and sometimes months.
It is not the magical formula of exactly what to eat that will lead to weight loss. It could be numerous formulas that will lead to weight loss. But most humans will not be able to sustain that for long term. As a dietitian, I don't have the hidden knowledge of the secret foods that do it. But as a dietitian who understands the research, I do know how we can eat to improve our health--whether or not weight loss will be a side effect.
If someone wants me to tell them exactly what to eat to lose weight, now I am less sure than ever that I can help them. But someone who is concerned about their health....that's what I can do.