The effect of intermittent energy and carbohydrate restriction v. daily energy restriction on weight loss and metabolic disease risk markers in overweight women.
Level 2 - randomized trial
Individual randomized controlled trial
PubMed 23591120 · doi:10.1017/S0007114513000792
What was done
Overweight women (n = 115, aged 20 to 69 years with a family history of breast cancer) were randomized to an overall 25% energy restriction for a 3-month weight-loss period followed by a 1-month maintenance phase. The three arms were: intermittent energy and carbohydrate restriction (IECR: 2500-2717 kJ/d, <40 g carbohydrate/d for 2 d/week), daily energy restriction (DER: approximately 6000 kJ/d for 7 d/week), or IECR with ad libitum protein and fat (IECR+PF for 2 d/week). Maintenance was 1 d/week for the intermittent groups.
What was found
Insulin resistance decreased with IECR (mean -0.34 [95% CI -0.66, -0.02] units) and IECR+PF (mean -0.38 [95% CI -0.75, -0.01] units), with significantly greater reductions than DER (mean 0.2 [95% CI -0.19, 0.66] uU/unit, P = 0.02). Both intermittent groups achieved greater body fat reductions compared with DER (IECR: mean -3.7 [95% CI -2.5, -4.9] kg, P = 0.007; IECR+PF: mean -3.7 [95% CI -2.8, -4.7] kg, P = 0.019; DER: mean -2.0 [95% CI -1.0, 3.0] kg). During the 1-month maintenance phase, 1 d/week of IECR or IECR+PF maintained the reductions.
Why it matters
Intermittent restriction of energy and carbohydrates two days per week may be more effective for reducing body fat and improving insulin resistance than standard daily calorie cutting in the short term.
Limits
The trial included only women with a family history of breast cancer, limiting generalizability to men and other populations. The follow-up was short (3 months of restriction, 1 month maintenance), and long-term adherence and safety were not established.
Cited by
- supports In a study of 100 overweight women at risk for breast cancer by Michelle Harvie and Dr. Mattson, both 5:2 fasting and daily 25% caloric restriction led to ~8% weight loss over 6 months, but 5:2 fasting caused greater improvements in insulin sensitivity and greater loss of belly fat.
- supports In a clinical trial by Michelle Harvie, women on a 5:2 intermittent fasting diet lost more abdominal fat and had significantly greater improvements in insulin sensitivity than women on daily calorie restriction with identical total weight loss and calorie intake over 6 months.