Rationale for novel intermittent dieting strategies to attenuate adaptive responses to energy restriction

Abstract

Eating patterns involving intermittent energy restriction (IER) include 'intermittent fasting' where energy intake is severely restricted for several 'fasting' days per week, with 'refeeding' days (involving greater energy intake than during fasting days) at other times. Intermittent fasting does not improve weight loss compared to continuous energy restriction (CER), where energy intake is restricted every day. We hypothesize that weight loss from IER could be improved if refeeding phases involved restoration of energy balance (i.e. not ongoing energy restriction, as during intermittent fasting). There is some evidence in adults with overweight or obesity showing that maintenance of a lower weight may attenuate (completely or partially) some of the adaptive responses to energy restriction that oppose ongoing weight loss. Other studies show some adaptive responses persist unabated for years after weight loss. Only five randomized controlled trials in adults with overweight or obesity have compared CER with IER interventions that achieved energy balance (or absence of energy restriction) during refeeding phases. Two reported greater weight loss than CER, whereas three reported similar weight loss between interventions. While inconclusive, it is possible that achieving energy balance (i.e. avoiding energy restriction or energy excess) during refeeding phases may be important in realizing the potential of IER.

Intermittent Energy Restriction Attenuates the Loss of Fat Free Mass in Resistance Trained Individuals. A Randomized Controlled Trial

“…Some have postulated that achieving energy balance (or the absence of energy restriction) appears to be important in order to attenuate the effects of the adaptive responses to energy restriction [1,39]. A number of investigations have reported that participants consume less than their weight maintenance energy requirements during refeeding days, and subsequently are in varying degrees of energy restriction for the duration of the intervention [1,6,40,41]. In a comprehensive review on this topic, Sainsbury and colleagues [1] summarized all known randomized controlled trials in overweight/obese adults in which energy balance was intermittently restored.…”

“…A number of investigations have reported that participants consume less than their weight maintenance energy requirements during refeeding days, and subsequently are in varying degrees of energy restriction for the duration of the intervention [1,6,40,41]. In a comprehensive review on this topic, Sainsbury and colleagues [1] summarized all known randomized controlled trials in overweight/obese adults in which energy balance was intermittently restored. Of these five investigations, two resulted in greater weight loss in the intermittent energy restriction than in the continuous energy restriction [9,42] and the three others reported that weight loss was comparable between intermittent energy restriction and continuous energy restriction [43][44][45].…”

“…The conventional approach for weight loss is adherence to a daily restriction of energy intake to levels that are below weight maintenance requirements for an extended period of time [1]. While this practice is successful for short-term weight loss, the human body responds to chronic energy restriction and weight loss with a range of adaptive metabolic, behavioral, and endocrinological responses that make continued weight loss difficult [1][2][3][4]. A reduced energy expenditure greater than that expected from the reduction in body mass [5] is one of the most studied aspects of the body's adaptive responses to continued weight loss.…”

“…'Non-Linear Dieting' (also known as intermittent energy restriction) can be utilized as a strategy to attenuate this adaptive response, thereby increasing weight loss during subsequent periods of energy restriction [1]. Non-linear dieting involves intermittent periods of energy balance throughout the diet, as opposed to continuous long-term energy restriction.…”

Time restricted feeding for the prevention and therapy of lifestyle-dependent diseases: Results of a pilot study in a pre-post design

“…All concepts of intermittent fasting described here, however, have in common a reduced calorie intake on certain days. Altogether, successful intervention studies are available for these fasting forms, which confirm their effectiveness (6). However, a certain degree of willpower and discipline is required for a consistent performance.…”