It has similar weight loss and maintenance outcomes to continuous energy restriction, Australian research says.
For adolescents with severe obesity needing intensive treatment to manage comorbidities, intermittent energy restriction is an effective alternative to a continuously low-calorie diet.
Evidence shows early weight loss has better long-term outcomes, but the most effective treatments for severe obesity – bariatric surgery and pharmacotherapies – can be difficult to access and expensive.
Therefore, behavioural therapies, which are recommended in the guidelines, need to be effective, say the authors of an Australian study published in JAMA Pediatrics this month.
Intermittent energy restriction offers an additional behavioural weight management option, with the same benefits as continuous very-low energy diets, they say.
The trial, conducted at the Children’s Hospital at Westmead and the Monash Children’s Hospital, involved 141 adolescents aged 13-17 with a BMI of 30 or higher and at least one cardiometabolic complication, including prediabetes, insulin resistance, acanthosis nigricans, hypertension, low high-density lipoprotein cholesterol (HDL-C) level, high level of triglycerides, elevated alanine transaminase or γ-glutamyl transferase level, or polycystic ovary syndrome.
All the teenagers first went on a very low energy diet for four weeks (800kcal/d).
At week five, one group (71) then followed an intermittent restriction diet, where they could eat 600-700kcal per day for three days per week, alternated with four days of healthy eating but no calorie restriction. The other group (70) had a restriction on the number of calories consumed per day, depending on age (1430-1670 kcal/d for 13-14-year-olds and 1670-1900 kcal/d for 15-17-year-olds).
They were given detailed diet plans, a daily multivitamin. They were seen by a dietician in person at three-weekly intervals, then less frequently, and supported via provided via phone, text message, or email.
Only those who reached a BMI of 25 had any dietary change, moving to weight maintenance, rather than loss.
After a year they found teenagers in both groups had reduced their body weight – average BMI reductions of 1.62 for intermittent fasting and 1.53 for continuous restriction – and their fat mass index. There were no significant differences between the two groups in body composition or cardiometabolic outcomes: both groups saw reductions in blood pressure percentiles, concentrations of total cholesterol, triglycerides, and fasting plasma insulin.
Improvement in insulin resistance only persisted at week 52 for some in the continuous restriction group.
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About 60% of the intermittent group and 77% of the continuous restriction group completed the year. Three of the intermittent group and 10 of the continuous group reported gastrointestinal disturbances. One in the continuous group developed gallstones and had a cholecystectomy. One in the intermittent group developed atypical anorexia nervosa.
More participants withdrew from the intermittent group than from the continuous group because they didn’t want to continue with the diet, the authors said.
“These results contrast with our hypothesis that IER would be more acceptable and lead to better weight loss compared with CER for adolescents with obesity-associated complications.”
“Indeed, our 6-month pilot study examining IER reported that adolescents with obesity liked the intervention, and given the opportunity at 12 weeks to continue IER or transition to a continuous energy diet, all (n = 23) chose to continue with IER.”
Although 117 (83%) of the participants were Australian born, 40% spoke a language other than English at home. The group also included two people identifying as Aboriginal and Torres Strait Islander, six people born in India, two in Vietnam, and nine in other unspecified countries. Most had a family history of obesity (97) or diabetes (117).
“The findings of this trial suggest that for adolescents with obesity-associated complications, IER can be incorporated into a behavioral weight management program,” the authors conclude.
The kind of program recommended by the guidelines would involve 26 hours of nutrition, physical activity, and preferably in-person behaviour change lessons for three to 12 months.
