Weight loss is easier if you can somehow quantify and measure what you need to do to achieve your goal weight. The science is actually pretty simple. It revolves around calories (a measurement unit for energy).
Your body needs energy to survive, and it gets that energy from food. Eating is good - it gives you the calories you need to live. But the problem is, if you eat more calories than your body needs, these extra calories are stored by your body. Over time, storing calories in this way makes you gain weight. If, on the other hand, you burn more calories than you eat, you will slowly lose weight.
Figure out how many calories your body needs daily (your Basal Metabolic Rate, BMR). You can use the Mifflin St Jeor equation to do that and apply a physical activity level multiplier based on your lifestyle. A quick trip to Wikipedia should give you the information that you need.
Then, if you want to lose weight, set a net daily calorie target of, around 500 calories less than your BMR. If you don't exercise, you can consume that amount in a day. If you exercise, you can "eat back" the calories burned through exercise. As long as you hit your calorie target, you will lose weight. You should not set a target that is too low though, since your body will go into starvation mode and your metabolic rate will drop, meaning that your body needs less energy to survive. So, once you set your target, aim to hit it, as opposed to trying to come in as far under the target as possible.
Note that everybody is different, so the target that you calculate may need adjustment. If you find that you're not losing weight after two weeks of consistently hitting your target, revise your target down by say 200 calories.
So, build an awareness of how many calories you're taking in from food versus how many calories you're burning through your lifestyle and exercise. It doesn't matter what you're eating as long as you hit your net daily calorie target. You can actually eat whatever you want. The trick is portion control.
The science is pretty simple. However, the challenge is twofold:
1) You need to know how many calories you're taking in through food, and you need to know how many calories you're burning through exercise.
2) You need to keep track of the above.
In my personal opinion, the most convenient way to do that is to use a mobile app. There are several out there. A search for "calorie counter" should bring up the most popular ones. Most of these apps come with a built in food database. You search for what you eat, and how much of it, and the app knows how many calories you've consumed. Some calorie counting apps are able to estimate how many calories you burn through exercise as well. While evaluating them, compare features and ease of use, but bear in mind that the app will only be as accurate as the database that it relies on.
Disclaimer: I'm not a dietician! I'm an app developer and the company I work for is in the weight loss field. But I'm not a dietician. Use the above information as a starting point for your own research :-)
Disclaimer 2: This post does not reflect my employer's opinion. Only my own.
