Evidence from existing RCTs is relatively
consistent with regard to the role of exercise
in producing weight loss, either when used
alone or in combination with dietary modification.
Although the majority of RCTs show only
modest weight loss with exercise alone, in most
of these studies the level of exercise prescribed
was relatively low and would have produced
an energy deficit far smaller than that usually
recommended for weight loss by caloric restriction.
The resulting weight-loss findings from
these studies are, therefore, consistent with the
amount of exercise prescribed. Although other
studies demonstrate that it is possible to achieve
significant weight loss with high levels of physical
activity alone (when the volume of exercise
prescribed is equivalent to the energy deficit
usually recommended for weight loss by caloric
restriction and energy intake is held constant),
producing the amount of activity needed is challenging
given the difficulty of getting sedentary
people to achieve and consistently adhere to
increased physical activity.