No, you must mantain both for effective wight loss.You must follow calorie restriction too.To optimize weight loss, a combination of diet and exercise is best, and that exercise alone will not  be sufficient to control body weight.Try to modify your diet plan such as:

*Eat six smaller meals throughout the day rather than the traditional 3 large meals. By eating small meals or snacks every three hours you will maintain a steady blood sugar level and will avoid energy highs and lows. Replacing junk food with complex carbohydrates such as whole grains and raw leafy vegetables will make a big difference as well.

*You often see serving sizes listed on food labels. They aren't a recommendation of how much you should eat, but are simply the amount of food on which the product's nutritional analysis is based. This information allows you to compare the nutritional value of one product with that of another.

*Look for "USDA Choice" or "USDA Select" grades of beef rather than "USDA Prime," which usually has more fat content.
When buying ground beef, look for packages with the lowest percentage of fat — 15 percent or lower. Most stores offer several types of ground beef with varying percentages of fat by weight.
Avoid beef that has streaks of fat throughout (marbled). Instead, buy meat with the least amount of visible fat.

In this way you can make a proper plan for diet control

You can get more about this topics under the following link ...

http://www.ndri.com/article/diet_restriction_or_exercise_which_one_is_effective_for_weight_loss-84.html

Hope you could get a idea and enjoy a healthy life.