It is because the body adjusts and adapts to the caloric shift (assuming one is using a traditional calorie deficit weight loss program).
The longer you are on it, the harder it is to lose weight.
Here is an example that will help you understand why the pounds come off slower.
When an overweight person cuts down significantly on what he eats, the body defends itself by using fewer calories. The effect can be long-lasting: If a person’s weight drops to 150 pounds from 250, significantly fewer calories must be consumed daily to stay at that weight than would be necessary if the person had never been overweight.
Even if a 170-pound person loses 20 pounds, he needs 15 percent fewer calories to maintain the new weight than someone who always weighed 150. Short of bariatric surgery, very gradual weight loss — say, no more than 20 pounds a year — may be the a way around this metabolic slowdown. This strategy gives the body and appetite a chance to adjust.
An alternative is to exercise which will increase metabolism instead of just relaying on calorie reduction to manage weight.
Another strategy is to replace some starchy foods with protein sources. This simple swap of calories makes it easier to manage weight because protein requires more calories to be broken down and used for fuel.
Strength exercises, if done properly, can also help you add or increase the muscle fibers in your body. These fibers require more calories. Effectively the muscle consumes calories that would be normally stored as fat. Thus keeping you leaner, stronger and healthier. Healthier because your body fat would be lower.
There are ways to reset or wisely manage your metabolism, but it usually requires a game plan and a dose of commitment.
Stay healthy, my friend.
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