Your body needs energy to keep your organs going and to move around. You get energy by consuming calories. If you don't consume enough calories, the body burns energy using your fat.
If you take one pound of fatty flesh, burn it, and convert it into energy, you get about 3500 calories. Hence, why diet books like to tout the advice, "burn 3500 calories to lose one pound of fat."
Unfortunately, it's not that simple. A person never loses weight at one constant rate. Mathematical models have been created to demonstrate that fact. When mapping weight loss, it's always going to curve from one steady state down to another (more like a parabola).
Now, let's say the 3500 rule is true and you lose weight at a constant rate. By that logic, you could lose 52 pounds in a year by cutting back 500 calories a day (3500 calories per week). By that same logic, after ten years, you would lose 500 pounds. If you don't have 500 pounds to lose, you won't live through the process. So, the rule breaks down way before you get to that point.
Larger people burn more energy because it takes more energy to move a larger mass. If you lose weight, your body will need less energy because there's less tissue to power. Thus, you'll never lose weight at a constant rate by cutting the same amount of calories. You'll go from one steady state to the next as your body metabolically adapts to each new diet.
No one wants a slow diet, but a slow diet is an effective weight loss option. According to the video, by cutting back on just 100 calories a day, you should see the full effect of your diet in three years time.
Other diet tips include cutting back on added sugar. Sugar is made up of glucose and fructose. While every cell in our body can metabolize fructose, only our liver can metabolize glucose. If the liver has already stored the maximum amount of glycogen (the stored form of glucose), the excess glucose gets turned into fat. Also, added sugar is high in calories but low in nutritional value. Focus on getting the most nutritional value out of your calories.