Eating less means ingesting less calories, and as a result the human body is forced to burn stored fat. Imagine the human body is just like a bank account. The less money (calories) in the account, one might have to borrow to get more cash. The analogy is the same with the human body. The less food that is consumed, the more fat is burned, as the body has to get the energy from somewhere in order to function.
Even though someone who wants to lose weight consumes nothing but healthy food, if that person overeats, then the excess food is going to be stored as fat in the body. Of course, it is more “healthy” to consume nutritious and healthy food, but it’s the amount of that food that determines how much of that food is stored as fat. A good example is if someone limits themselves to one thousand calories per day.
Even though it would be extremely unhealthful to eat nothing but sweets until that person reaches one thousand calories, the point is that if that person burns two thousand calories per day, one thousand of those calories are going to be “borrowed” from the fat on the body in order to function. In effect, that person will be running a deficit of one thousand calories per day, even though the food consumed isn’t “healthy”.
The point is, it would be better nutritionally for the same person to eat one thousand healthy calories per day, (fruit, whole grains, etc.), and still run the same deficit, but gain the additional advantage of consuming the proper nutrients the body needs. Lost weight is the result in both cases, but it’s more healthful to eat the proper food in the long run.
When the question arises as to which is faster losing weight, eating sweets as opposed to healthy food, there really isn’t much difference in the short run. But when talking about the long run, of course it’s better to eat healthy, as at least the body is getting the vitamins and minerals it needs to operate successfully.
So time doesn’t have to do too much in the equation as far as what style of eating is speedier. However, the important point to stress is that losing weight means changing behavior, as diets typically aren’t successful over time. What is successful is changing eating patterns (according to Weight Watchers), and incorporating a healthy eating and exercise regimen that one can stay with over time. And speaking of time, eating in a healthy manner will enable one to lose weight and keep the weight off in the long run.