Answer:

The bottom line to weight loss is burning more calories than you eat. This simple energy equation applies: calories in vs. calories out (the behavior isn't always simple, but the equation is). If you eat 2,500 calories a day and only burn 2,000, you gain weight; if you eat 1,500 calories and burn 2,000, you lose weight; if you eat 2,000 and burn 2,000, you maintain weight. There are no exceptions. It is true that some medical conditions (e.g. menopause, adrenal abnormalities), medications (e.g. antidepressants), and smoking cessation (average weight gain of 9-12 pounds) can make weight loss difficult, but even if one of those factors applies to you, you still need to eat fewer calories than you burn to lose weight.

As for exercise, no matter how much you do, you still will not lose weight if you eat more than you burn. People lose weight all the time without exercise by reducing their caloric intake, but keeping your weight off without exercise is another story. Exercise appears to be the single best predictor of long-term weight maintenance. But again, no matter how much exercise you do, you won't lose weight if you eat more than you burn. In studies where people are told to lose weight with exercise or diet, the dieters ALWAYS lose significantly more weight. In fact, the exercisers generally lose only a few pounds, or none at all.

With that said, if you're not losing weight, it has to be that you are eating more calories than you burn. This is true no matter how much exercise you do.

As for fitness, your fitness will improve whether you lose weight or not, and as you continue you will notice improvements in strength and tone and endurance even if the scale doesn't show improvement.