An increase in metabolism is important in order to continue to lose weight. Metabolism is important because it helps us burn calories necessary to promote a healthy weight.
If we have problems with our thyroid which regulates metabolism we could have metabolism reactions such as increased weight gain or the inability to gain weight.
People with a hypothyroid have a slower than average metabolic rate and tend to gain weight easily.
These people usually have to have their thyroid checked and need to use medication to create a normal metabolic rate. In addition, they are usually asked to exercise daily and avoid foods laden with sugar or those that are highly processed.
These types of foods tend to slow the metabolism even more which is why they need to be avoided.
Those afflicted with a hyperthyroid have the opposite problem. They seem to be able to eat whatever they want without ever gaining weight. People afflicted with this condition are usually underweight because their metabolic rate is so fast that they have difficulty gaining weight despite their caloric intake.