How are metabolism and nutrition related to disease?

As an example, if a person's diet consumption contains a lack of fuel for energy, this causes their metabolism to slow down therefore leading to weight gain. Becoming overweight increases the risk of health diseases such as obesity, cardiovascular disease etc. Not sure if this helped but this was just based off my current knowledge :)

People who utilizes the progression principle will ensure their exercise program increases in frequency, intensity, time, and type. the changes need to happen gradually in order to ensure they make gains in their fitness program. a person who doesn't utilize the progression principle can still gain health benefits from exercising, but will not continue to improve in cardiovascular fitness.