Rate of weight loss and body composition: does “slow and steady” win the race?

Obesity^[1] has been described as a public health crisis, with its prevalence increasing in many parts of the world. Since obesity increases the risk of numerous health conditions^[2], it’s no surprise that it has been associated with a lower quality of life^[3] and a reduced life expectancy^[4]. Importantly, sustained modest weight loss of 5-10% can reduce^[5] the incidence and progression of a number of health conditions associated with obesity. As such, several dietary weight loss strategies have been developed and tested over the past few decades. What all of them have in common is that they place the participant in a negative energy balance in order to achieve weight loss.

While the goal of weight loss dietary interventions is to reduce bodyweight through energy restriction, experts have yet to reach a consensus regarding the degree of energy restriction and rate of weight loss that will result in the best possible long-term outcomes. On the one hand, diets that severely restrict energy intake have been found to result in significantly greater short^[6]- and long-term^[7] weight loss compared to diets that moderately restrict energy intake. On the other hand, some research has reported that severely energy-restricted diets may result in greater losses in lean body mass^[8] and larger risk for weight regain^[9] compared to moderately energy-restricted diets, while other research has detected no effect of the size of the energy deficit on changes in lean body mass^[10] and risk for weight regain^[11].

Although studies like the ones mentioned above have tried to shed light on how the degree of energy restriction and rate of weight loss may affect body composition, the available research to date suffers from a number of limitations. For example, the aforementioned studies were not randomized clinical trials, were of short duration, or were not specifically designed to measure changes in body composition as the primary outcome. The study under review aimed to address these limitations by directly comparing the long term (longer than six months) effects of severe vs. moderate energy restriction on body composition in postmenopausal women with obesity.

Current dietary guidelines emphasize the importance of weight loss in people with overweight and obesity for improving health outcomes. However, the degree of energy restriction and rate of weight loss that will result in the best possible long-term body composition outcomes is still being debated. The study under review aimed to investigate the long term (longer than six months) effects of severe vs. moderate energy restriction on body composition in adults with obesity.