The law of conservation of energy states that the energy in a system will remain constant over time. Energy cannot be created or destroyed, it can only move from one place to another. This is an important principle when applied to weight loss. It essentially means that if you burn more calories than you eat you will lose weight.
Most people think that the types of food you eat will impact your weight. In reality, the type of food you eat is less important than the amount (of calories). The above video helps to illustrate this important principle. Dr. James Painter is a nutritionist who created a documentary called Portion Size Me. In the film, he takes a group of students and has them eat only fast food for breakfast, lunch, and dinner. At the same time he controlled the quantity of calories they ate so they burned more than they took in. In the end all the students lost weight in spite of eating only junk food.
Of course, I cannot in good conscience recommend that you eat only fast food (for a variety of health reasons). I am merely trying to emphasize an important point. From the standpoint of weight loss the problem with junk food and fast food is that you get way too many calories way too fast without realizing it. This was illustrated by the focus group in the video above. When the subjects were not conscious of what they were eating they took in twice as many calories without knowing. Both groups felt satisfied with how much they ate but one group ate twice as much.
This is the reason it is nearly impossible to lose a significant amount of weight without controlling or (even better) counting the calories you take in. If you’re not doing this, significant and sustained weight loss is not likely to be successful.
I personally use a website called myfitnesspal. The site is available on my smart phone or any internet connection. It calculates how many calories a day I have to eat. I enter my height, weight, daily activity level, and how many pounds I want to lose each week. The site then calclulates how many calories a day I have to eat to meet my goals. The website has a database of thousands of foods including restaurant items. I enter what I eat and the program subtracts from my totals. There are many similar programs out there and I highly recommend that you use one. You will probably be surprised how many calories you are eating without even realizing it.
The bottom line is:
If you’re not counting, you’re probably not losing.