Effect of intermittent compared to continuous energy restriction on weight loss and weight maintenance after 12 months in healthy overweight or obese adults

Background and Objective Intermittent energy restriction (IER) is an alternative to continuous energy restriction (CER) for weight loss. There are few long-term trials comparing efficacy of these methods. The objective was to compare the effects of CER to two forms of IER; a week-on-week-off energy restriction and a 5:2 program, during which participants restricted their energy intake severely for 2 days and ate as usual for 5 days, on weight loss, body composition, blood lipids, and glucose. Subjects and Methods A one-year randomized parallel trial was conducted at the University of South Australia, Adelaide, Australia. Participants were 332 overweight and obese adults, ages 18-72 years, who were randomized to 1 of 3 groups: CER (4200 kJ/day for women and 5040 kJ/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 (2100 kJ/day on modified fast days each week for women and 2520 kJ/day for men, the 2 days of energy restriction could be consecutive or non-consecutive). Primary outcome was weight loss, and secondary outcomes were changes in body composition, blood lipids, and glucose. Results For the 146 individuals who completed the study (124 female, 22 male, mean BMI 33 kg/m(2)) mean weight loss, and body fat loss at 12 months was similar in the three intervention groups, -6.6 kg for CER, -5.1 kg for the week-on, week-off and -5.0 kg for 5:2 (p = 0.2 time by diet). Discontinuation rates were not different (p = 0.4). HDL-cholesterol rose (7%) and triglycerides decreased (13%) at 12 months with no differences between groups. No changes were seen for fasting glucose or LDL-cholesterol. Discussion and Conclusion The two forms of IER were not statistically different for weight loss, body composition, and cardiometabolic risk factors compared to CER.