Do we really need to exercise? Sometimes even the thought of it seems hard. The truth of the matter is that you'll be a healthier person for it and not just in terms of cardiovascular fitness. Exercise prevents disease. As an active person, you're less likely to develop cardiovascular disease, type 2 diabetes and osteoporosis, have a stroke or get certain types of cancers, such as colon and breast cancer. Physical inactivity is ranked just behind cigarette smoking as a cause of ill health.