Q: if having a calorie deficit is not helping one lose fat what should one do? There is no guarantee that increasing this deficit will help either.

A: You're completely correct. Most diet plans eventually run into this situation. Your body eventually adapts to whatever diet you put it on and after some time the fat loss grinds to a halt. If at that time you are still eating a good amount of food, you can try cutting down portion sizes further and that'll carry fat loss for a while longer. If, however, you are already eating very little (1500 calories per day or less, as a rule of thumb. or 1200 calories for petite women), then cutting the calories down further won't give you any results and may well jeopardize your health.

At a point like that you have to find ways to boost your metabolism. As usual, there are two ways of doing it. One is whole-body weight training -- if you haven't been doing it before, it's never too late to start. It will boost your metabolism right off the bet and will continue to do so as you gain new muscle (which, as a beginner, you will be able to do even under caloric deficit for some time).

If you already are weight-training, then you can still do something to give your metabolism a jolt: take a week or two off gym and then get back into it. You should especially do it if you haven't had a break from the gym in a long time. But this will not usually give you dramatic results, so you may well need to resort to the last option...

Eat more! Eating is still the greatest metabolic booster we know of. If your metabolism is deep asleep, you need to wake it up and nothing can do it as well as some extra food. There are two ways you can implement this approach:

• Pick 1-2 days out of the week which will be your serious eating days. During those days you'll make an effort to eat quite a bit more than usual. You won't lose any weight during those days, of course, but they will boost your metabolism for the rest of the week. Some people people structure their diets around this concept, which also allows them to have a built-in 'cheat' day when they eat whatever they want. I wouldn't recommend going on ice cream binges on these days, but do eat a lot more than usual.
• Go on a mini-bulk for a few weeks or even months. In this case you will actually eat enough to gain weight (and muscle! Don't forget to weight-train) for some time. At the end of this mini-bulk, you might have gained 5-7 pounds of which 3-5 are muscle and your metabolism will be much higher. Then you'll be ready to start on a fat-burning diet again.

Both of these boost-metabolism-by-eating-more approaches work and deciding which one to use is up to you. With the second approach keep in mind that you will actually gain some fat during your mini-bulk, but it will be worth it as you build muscle and boost your metabolism. Gain weight slowly, as always, to minimize fat gains. I personally prefer the second approach, but as I said, both are legitimate methods to boost your metabolism. Hope that gave you some ideas how to get out of a diet dead-end!