Calories Queen 
Intermittent fasting and body composition: After over a decade of research, where are we today?
Alternate-day fasting
Involves a 24-hour fasting period alternated with a 24-hour feeding period.Complete compensatory intake on the feeding days (to offset the fasting days’ deficit) does not occur, and thus total weight loss and fat loss occurs on ADF.
Study 1 -
Lean mass-retention has been an intriguing effect of ADF reported by Varady et al -~25% of maintenance requirements, typically in the form of a single meal at lunchtime) alternated with a 24-hour ad libitum (as desired) feeding period.
Study 2 -
Lean mass loss in ADF conditions has also been observed by other investigators.However, the effect might be attributable to more severe energy deficits.
Alternate-week fasting
one week on ~1300 kcal/day, one week on the usual diet
Has only a single study to-date, but is worth mentioning since it was as effective as continuous energy restriction for reducing body weight and waist girth at 8 weeks and 1 year.
Whole-day fasting
WDF involves one to two 24-hour fasting periods through the week of otherwise maintenance intake in order to achieve the deficit. Not all WDF studies involve zero energy intake in the ‘fasting’ days.
Study 1 :
Harvie et al saw no difference in bodyweight or body fat reduction between the WDF (2 ‘fasting’ days of ~647 kcal) group and controls when the weekly energy deficit was equated over a 6-month period.
Study 2 :
A subsequent study by Harvie et al compared two WDF diets (one with 2 structured energy-restricted ‘fasting’ days and one whose 2 ‘fasting’ days consisted of ad libitum protein and unsaturated fat) with daily energy restriction (DER).
Both WDF diets caused greater 3-month fat loss than daily energy restriction. An important detail here is that at 3 months, the 70% of the fasting days were completed in the WDF groups while the DER group achieved their targeted caloric deficit only 39% of the trial.
Time-restricted feeding
involves a fasting period of 16-20 hours and a feeding period of 4-8 hours daily. The most studied form of TRF is Ramadan fasting, which involves approximately 1 month of complete fasting (both food and fluid) from sunrise to sunset.
Study 1:
Unsurprisingly, significant weight loss occurs, and this includes a reduction in lean mass as well as fat mass.
Study 2:
Stote et al compared 1 versus 3 meals per day in eucaloric (weight–maintenance) conditions for 8 weeks and surprisingly found 1 meal resulted in fat loss and lean mass gain, while no significant improvements were detected in the 3-meal group. Unfortunately, the use of bioelectrical impedance (BIA) keeps these results questionable.
Study 3 :
Young et al found no significant differences in weight loss and body composition change between 1, 3, or 6 meals per day.
Frequency of feeding, weight reduction, and body composition. - PubMed - NCBI
Others :
-
The Warrior Diet
It involves a 4-6 hour feeding period at night, and an 18-hour “under-feeding” period during the day. The diet draws inspiration and justification from the purported habits of our Stone Age ancestors, as well as other leaps of faith involving the sympathetic and autonomic nervous system.
-
Berkhan’s Leangains system
16-hour ‘fasting’ period and an 8 hour feeding period.16 What separates this protocol from others is its attention to macronutrition, and its administration of branched chain amino acids (BCAAs) during the fasting period.
Systematic Reviews :
-
#1 Systematic Review
Total Studies : 40 studies in total, 12 of which directly compared an IER with a CER condition.
- They found that overall, the two diet types resulted in “apparently equivalent outcomes” in terms of bodyweight reduction and body composition change.
- In addition, neither IER or CER was superior to the other at improving glucose control/insulin sensitivity.
- No different effects on thyroid, cortisol, and sex hormones were seen between IER and CER, though the authors concede that there’s insufficient research comparing neuroendocrine effects of the two diet types to draw definitive conclusions in this area.
- Interestingly, IER was superior at suppressing hunger. The authors speculated that this might be attributable to ketone production in the fasting phases. However, this effect was somewhat immaterial since it failed to translate into superior improvements in body composition or greater weight loss.
Limitations :
- 14 of the 40 studies were by the same research group (Varady et al, University of Illinois at Chicago). Varady has published The Every-Other-Day Diet
- there’s a severe lack of IER (and IER vs CER) studies that include a structured training component.
-
#2 Meta Analysis
Methods : 6 studies on overweight or obese (BMI ≥25 kg/m) adults (≥18 years) on IF for 3-12 months.
- intermittent energy restriction was more effective than no treatment for weight loss ,however, this should be interpreted cautiously due to the small number of studies and future research is warranted to confirm the findings of this review
- the pooled estimate for studies that investigated the effect of intermittent energy restriction in comparison to continuous energy restriction revealed no significant difference in weight loss
- Intermittent energy restriction was comparable to continuous energy restriction for short term weight loss in overweight and obese adults
Limitation:
- High attrition (drop-out) rates were seen in the intermittent energy restriction (IER) groups. Attrition was high overall
- The subjects in this review were predominantly women
- The duration of the interventions was short (average duration: 5.6 months
- structured exercise regimens were lacking in the studies included in this review
IER and CER resulted in “apparently equivalent outcomes” for bodyweight reduction and body composition change. Given the complexity of weight management, it is unlikely that a ‘‘one size fits all’’ approach will work. IER may provide an alternative approach for individuals who struggle with daily energy restriction.
What about muscle gain?
No IF studies in the current literature have focused on the goal of gains in muscle size and/or strength. As such, No IF studies to-date have included a structured, progressive resistance training program.
It’s plausible that folks with the goal of maximizing rates of muscle gain should look to a minimum of 4 daily doses of protein at of at least 20-40 g (older subjects require 35-40 g to maximize the anabolic response
Conclusion
Is it effective? IF has proven itself to be an effective approach to dieting, and has outperformed conventional dieting in some cases.
Who should use IF? IF is best applied to goals oriented toward altering body composition and clinical markers that occur alongside body fat reduction This is not to say that muscle gain cannot occur with IF – it’s just that the rates of gain will not likely be maximized.
Which IF to do? As for which IF variant to chose (ADF, WDF, TRF, etc), they all have demonstrated effectiveness in the literature, and therefore can be chosen on the basis of personal preference.
Does intermittent fasting raise eating disorder risk?