i have never try keto but i have tried a lot of other diets. the key will always be balance and at the same time it's simple math. Your organism burns a x amount of calories per day so if you count what you eat there is no way not to lose weight. If you combined it with exercise it would be even better.

The reason why mostly everyone that follows a diet is gaining back the weight is that the initial diet wasn't for him, either he/she was missing the foods that liked, or portion were small etc etc The key again is balance. Find foods that you like, limit as much as you can food very high on fats and everything will be fine.

Otherwise keep eating! you only live once :P