Exercise has very little effect on weight loss though certain exercises can sculpt the body into a more pleasing shape. Whenever there is a weight loss article, several people will say smugly ' it's just a question of calories in v calories out ' but of course it isn't. Far better your body gets it's calories from butter, for instance, than sugar. No account is taken of Insulin resistance and other factors that make some diets so restrictive that people give up.Ancel Keys has a lot to answer for.
It's a great pity the right of free speech isn't based on the obligation to say something sensible.
The thing with exercise is it builds lean muscle which in turn burns calories more effectively than other tissue, including fat
After resistance (weights or using a persons own body weight) training the metabolic rate increases and the burning of calories continue even after the session has finished. The weights dont need to be heavy and there is no need to go to a gym. Most of the exercises can be adapted to suit any level of fitness or restrictions due to injury or medical conditions
Low fat diets are not good for then body as Cass said, far better to eat more good fats and plenty of lean protein