The results of this study might surprise you. A daily energy restriction diet compared with intermittent energy and carbohydrate restriction: which one gives the best fat loss?
As weight loss professionals, you already know that one of the biggest challenges for your clients is compliance. Interesting research investigating two different approaches to energy restriction diets has explored the difference in weight loss results between intermittent energy and carbohydrate restriction compared with a daily energy restriction approach.
Nutrition study design
In this study, participants had their baseline energy requirements calculated based on basal metabolic rate and were randomly divided into three groups:
1. Daily energy restriction (DER)
Participants in this group were instructed to reduce their energy intake by 25% from their baseline energy requirements. They were prescribed a Mediterranean diet with the following macronutrient breakdown:
- protein – 25% of overall energy intake
- low glycaemic index carbohydrate – 45% of overall energy intake
- fat – 30% of energy intake (broken down as 15% monounsaturated fats, 8% polyunsaturated fats, and 7% saturated fat).
Members of this group were asked to compose their diet from five fruit and vegetable serves per day, nuts and seeds, wholegrain cereals, olive oil, fish and seafood, a moderate consumption of dairy products, poultry, eggs, lean red meat and processed meat.
2. Intermittent energy and carbohydrate restriction (IECR)
This group were also instructed to reduce their overall energy intake by 25%, but with a different method: for two consecutive days each week, participants were asked to restrict their energy consumption by 70% and limit carbohydrate intake to 40g.
During the restricted days, participants were asked to consume between 2,500 and 2,717 kJ which included approximately 250g of protein foods (such as lean meat, fish, eggs, tofu), three servings of low fat dairy foods (e.g. 195mL semi skimmed milk, 150g low fat yoghurt, 30g low fat cheese), four portions of low-carbohydrate vegetables and one portion of low carbohydrate fruit. They were also asked to consume at least 1,170 mL of low-energy fluids, and a multivitamin and mineral supplement.
During the other five days of the week, the study participants were asked to eat a Mediterranean-style diet meeting their daily energy requirements.
3. Intermittent energy and carbohydrate restriction plus protein and fat (IECR + PF)
A third group was also established, to test if the addition of unrestricted protein and fat made any difference to the results. This third group received identical instructions to the IECR group, but could additionally, on restricted days, eat unlimited lean meat, fish, eggs, tofu and mono-unsaturated and poly-unsaturated fats.
Both intermitted diets limited saturated fat to less than 10% of energy, and participants across all groups were advised to limit (but were not required to abstain) from alcohol.
After following one of the three diets for a three month period, all participants were asked for follow a diet to meet their energy requirement for a further month, but the ICER and the IECR + PF groups continued with one restricted day of energy intake per week.
Other study design elements
Participants were asked to gradually work towards increasing their physical activity, with the goal of reaching 5 sessions of 45 minutes of moderate activity per week.
A dietician provided diet and exercise advice and employed a range of behaviour change techniques to support each participant. In addition, participants received fortnightly phone calls, and attended monthly face-to-face appointments where measurements were taken and diet, exercise and behaviour goals were reviewed.
Study investigators measure compliance with the dietary interventions using a 7-day food diary, which was checked for completeness with the respondent. Also, both IECR groups were asked to record whether they had completed 0, 1 or 2 days of restriction each week. Hunger and appetite were measured, and physical activity was also assessed using 7-day activity diaries.
During the study, 23% of participants withdrew: reasons for this include family or work issues, unrelated personal illness, problems adhering to the diet and not responding to follow up contact. This withdrawal rate is comparable with many weight loss studies.
It should also be noted that participants were screened prior to commencing the study and were asked to trial the two-day IECR approach. Of the potentially eligible participants, 12% were unable to tolerate the trial and 6% felt they would not be able to tolerate the IECR diet if allocated to one of those groups. IECR is clearly not an approach that is feasible for everyone.
However, the results of the study were very interesting. Here is a snapshot:
- After 3 months, the IECR group had significantly greater reductions in serum insulin compared with the DER group
- After 3 months, all groups saw small decreases in serum leptin, total and LDL-cholesterol and reduced systolic and diastolic blood pressure
- Of the three groups, 65% of the IECR group, 58% of the IECR + PF group and 40% of the DER group achieved 5% or greater weight loss after 3 months
- Both IECR and IECR + PF groups saw significantly higher reductions in body fat (but waist, hip and bust circumferences were not significantly reduced compared to the DER group)
- After 3 months, IECR and IECR +PF groups were successfully undertaking 70% of their restricted days, whereas the DER group achieved only achieved their energy restriction goal on 39% of the time during the third month of the study.
- There were minimal changes in physical activity for all participants during the course of the trial.
An interesting aspect of this study relates to the behaviour of the IECR and IECR +PF groups during the 5 days that they were not required to restrict their energy intake. Researchers found that although participants in these groups were advised to eat according to their full energy requirements, average ‘non-restricted’ intake was 32% less than prescribed for the IECR group and 23% less for the IECR + PF group. It is possible that these actions also influenced the final results of the study.
The study is based on the premise that people have great difficulty achieving and maintaining weight loss though energy restriction. However, for those who can tolerate the approach, it appears that IECR might be a helpful strategy, with the benefit of increased sensitivity and higher body fat losses than might be achieved if following a daily energy restriction diet.
Harvie, M., Wright, C., Pegington, M., et al. (2013). The effect of intermittent energy and carbohydrate restriction v. daily energy restriction on weight loss and metabolic disease risk markers in overweight women. The British Journal of Nutrition, 110(8), 1534–47. doi:10.1017/S0007114513000792