Most people know that, in general, if you want to lose weight, you're going to have to eat less - and at that, eat less junk food and more whole foods. If weight loss is a function of how many calories you consume versus how many calories you expend, it makes sense to simply eat less and exercise more, right?
The big problem with all this is, as humans who don't have built-in calorie calculators, we have a tendency to underestimate how much we eat and overestimate how much we exercise.
So as a personal trainer, when I'm talking to someone who wants to lose weight and they tell me that they walk maybe a mile every day for exercise, I think to myself, "That's all?" Now, walking a mile is great, and depending on your size, you can burn about 100 calories doing that. But when you consider that many approximations list a pound of fat as 3,500 calories, a little walk won't seem like much.
You might be eating great foods and even counting your calories diligently, but if you're not matching your calories to your daily activity levels, you can end up throwing yourself off. Remember, it's not about picking an arbitrary number of calories to eat every day, but eating the right amount for YOUR personal lifestyle.
An example of this might be if I were working with a 150 pound woman who exercises 4 days a week and wants to lose weight. Based on her activity level and fitness goals, I'd start her off eating around 2,100 calories per day. On the flip side, if this same woman only does a minimal amount of exercise every week, because of her activity level, I'd recommend she consumes around 1,650 calories per day.
With all that said, what should you do if you've hit a slow point in your weight loss? You could simply lower your caloric intake to match your daily expenditure, but I would personally recommend bumping up your exercise days. Sure, the numbers might add up the same either way, but the benefits of exercise are more than just fat loss; exercise is known to boost energy levels, lower blood pressure, and increase bone strength, just to name a few. So enjoy the (appropriate) amount of food you're eating, just get out and move more!
And besides, who doesn't like a little sweat?
(Note: the caloric recommendations are calculated from formulas I learned in my certification courses. You can feel free to use a similar calculator online, such as this one. Keep in mind, these are starting points, and may need to be adjusted as you continue in your exercise.)