Does Timing Matter? A Narrative Review of Intermittent Fasting Variants and Their Effects on Bodyweight and Body Composition

Abstract

The practice of fasting recently has been purported to have clinical benefits, particularly as an intervention against obesity and its related pathologies. Although a number of different temporal dietary restriction strategies have been employed in practice, they are generally classified under the umbrella term “intermittent fasting” (IF). IF can be stratified into two main categories: (1) intra-weekly fasting (alternate-day fasting/ADF, twice-weekly fasting/TWF) and (2) intra-daily fasting (early time-restricted eating/eTRE and delayed time-restricted eating/dTRE). A growing body of evidence indicates that IF is a viable alternative to daily caloric restriction (DCR), showing effectiveness as a weight loss intervention. This paper narratively reviews the literature on the effects of various commonly used IF strategies on body weight and body composition when compared to traditional DCR approaches, and draws conclusions for their practical application. A specific focus is provided as to the use of IF in combination with regimented exercise programs and the associated effects on fat mass and lean mass.

Popular Dietary Trends’ Impact on Athletic Performance: A Critical Analysis Review

“…When looking at a 20:4 regimen and its impact on an 8-week resistance program no significant difference was noted in total body composition and the cross-sectional area of muscle [ 113 ]. Of note, it is important to maintain a resistance training regimen during TRE, as a robust narrative review conducted by Aragon and Schoenfeld demonstrated that without resistance training, many who use TRE as a dietary strategy lose lean muscle mass over time [ 114 ]. Studies have not assessed the specifics of the 5:2 diet in humans, but early mouse models showed an improvement in endurance [ 115 ].…”

Intermittent Fasting as a Potential Therapeutic Instrument for Major Depression Disorder: A Systematic Review of Clinical and Preclinical Studies

“…Ad libitum feeding cycles for 24 h alternated with 24 h of total fasting (no caloric intake). Modified alternate day fasting (25% of caloric needs maintained; consumption of approximately 500 kcal on "fasting" days) is the predominant type of IF in the literature [30,31] Two Days Fasting Two consecutive or non-consecutive "fast" days, followed by five days of ad libitum food (a 2-day fast is popularly known as a 5:2 fast) [32]. Fasting days can be either full fasting or keeping to 25% of caloric needs.…”

“…Fasting days can be either full fasting or keeping to 25% of caloric needs. Also, they can be consecutive or non-consecutive [31,32].…”

Keto Menu–Effect of Ketogenic Menu and Intermittent Fasting on the Biochemical Markers and Body Composition in a Physically Active Man—A Controlled Case Study

“…Certainly, all its mechanisms and detailed influence on the body are not yet known. The benefits are considered, inter alia, in the aspects of metabolic health, improvement of body composition [7,8], intestinal microbiota [9], cerebral metabolism [10], prevention of cardiovascular diseases [11], antitumour effects [12], and many other health aspects [13]. The fasting consists of temporary abstaining from eating.…”

“…The fasting consists of temporary abstaining from eating. Various variants are distinguished, including alternate-day fasting (ADF), which means fasting every other day; twice-weekly fasting (TWF), consisting of fasting for two days weekly; early time-restricted eating (eTRE), which means eating only for 4-10 h a day (usually 8 h) in the early daytime; and delayed time-restricted eating (dTRE), i.e., as in eTRE, but the eating window is shifted to later daytime hours [7].…”