I can understand the frustration of a diet not working. As we age, our metabolism slows down making it harder. We might be taking drugs, even OTC drugs, that interfere with weight loss. Even seemingly innocent things like NSAIDs can. HRT sure can. Statins (evil things) can. Thyroid issues, cortisol issues... and so on.

Even if you rule out all that, the human female metabolism can be stunningly resistant to weight loss.

The good news is that you can be healthy, happy and fit at a slightly higher weight than fashion dictates. That's where my focus is these days. I feel just awful when I mis-eat, so I am concentrating on eating as good as I possibly can and exercising (weight lifting, a bit of interval train... no hamster wheeling).