First, the answer to the question is...YES!
Speaking as a personal trainer, it is absolutely imperative to balance both exercise and diet. An imbalance will stress the body, causing the metabolism to slow. In turn, a dieting individual will have more difficulty maintaining a healthy weight during their life time.
When individuals diet by restricting calories alone, and do not incorporate exercise into their daily routine, muscle mass deteriorates. According to a research article published in the 2004 British Journal of Nutrition, author Hill states when caloric intake is restricted by 300 calories a day, the body will respond by gradually lowering the metabolism 20%.
However, the author states both cardio-respiratory / aerobic exercise and resistance training provides a protective mechanism against this 20% shift.
1) Work with a qualified personal trainer, email me at firstname.lastname@example.org for references.
2) Consider having your Resting Metabolic Rate analyzed with the Body / Med Gem (R). This is professional grade equipment and will provide accurate information on your resting metabolic rate. The results of the test will help balance calories consumed, to calories exerted. If you would like to make an appointment for a test email me at email@example.com.
3) Ensure you are incorporating effective cardio-respiratory and resistance training techniques into your routine.
4) Stress a healthy "diet" that focuses more on a balanced intake of foods, rather than a "diet" that restricts calories.