A recent study following the popular 5:2 IF schedule vs a calorie matched restricted calorie diet, yet again, found no statistically significant differences in endpoints studied, which was weight weight cardiometabolic factors:
“Intermittent energy restriction was as successful in achieving modest weight loss over a 24-month period as continuous energy restriction.”
The study ran a full year and followed over 100 people. The Abstract is posted blow.
Intermittent Fasting (IF) continues to be a popular approach to weight loss. It’s not a new approach, and most of my comments HERE still hold up. Since that vid, a number of studies in humans have been done, and the effects have not been impressive. The study below, the largest to date, that ran 50 weeks, did not find major differences in weight loss, and other endpoints looked at.
I’m not ready to dismiss IF per se, as there’s still more questions then answers. In this case, in obese non-exercising people, a 5;2 IF protocol was not superior to calorie matched diet for weight loss. The next step would be comparing different IF protocols. For example, perhaps the 5:2 approach may not potentiate endocrine adaptation as well as other approaches, or maybe different protocols will be more effective for different populations. Fact is, we don’t have the answers at this time, and what exists for human studies small and or short term.
Also, what impact does IF have on performance or strength? Does a strength or physique athlete respond differently to IF than say an endurance athlete? What about lean vs people with higher bodyfat levels? There’s still plenty of Qs to be answered regarding IF…
Bottom line at this time: find the approach you find most beneficial to your goals, but don’t fall for IF being a magical approach to fat loss, cuz it’s not. It’s still about the calories. Some recent thoughts on calories vs exercise worth a read HERE also as well as understanding the 3,500 calorie myth HERE.
Effects of intermittent and continuous calorie restriction on body weight and metabolism over 50 wk: a randomized controlled trial
The American Journal of Clinical Nutrition, Volume 108, Issue 5, 1 November 2018, Pages 933–945,
Background and objective
Intermittent energy restriction continues to gain popularity as a weight loss strategy; however, data assessing it’s long-term viability is limited. The objective of this study was to follow up with participants 12 months after they had completed a 12-month dietary intervention trial involving continuous energy restriction and two forms of intermittent energy restriction; a week-on-week-off energy restriction and a 5:2 programme, assessing long-term changes on weight, body composition, blood lipids and glucose.
Subjects and methods
109 overweight and obese adults, aged 18–72 years, attended a 12-month follow-up after completing a 12-month dietary intervention involving three groups: continuous energy restriction (1000 kcal/day for women and 1200 kcal/day for men), week-on-week-off energy restriction (alternating between the same energy restriction as the continuous group for one week and one week of habitual diet), or 5:2 (500 kcal/day on modified fast days each week for women and 600 kcal/day for men). The primary outcome was weight change at 24 months from baseline, with secondary outcomes of change in body composition, blood lipids and glucose.
For the 109 individuals who completed the 12-month follow-up (82 female, 15 male, mean BMI 33 kg/m2), weight decreased over time with no differences between week-on and week-off and continuous energy restriction or 5:2 and continuous energy restriction with −4.5 ± 4.9 kg for continuous energy restriction, −2.8 ± 6.5 kg for week-on, week-off and −3.5 ± 5.1 kg for 5:2. Total cholesterol reduced over time and glucose, HDL, LDL and triglycerides were unchanged.
Discussion and conclusion
Intermittent energy restriction was as successful in achieving modest weight loss over a 24-month period as continuous energy restriction.
Will Brink is the owner of the Brinkzone Blog. Will has over 30 years experience as a respected author, columnist and consultant, to the supplement, fitness, bodybuilding, and weight loss industry and has been extensively published. Will graduated from Harvard University with a concentration in the natural sciences, and is a consultant to major supplement, dairy, and pharmaceutical companies.
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