Limited success of traditional weight loss interventions

Traditional weight loss interventions focus on avoiding “fattening foods”. People following this type of approach need to increase their cognitive dietary restraint (CDR) which refers to the tendency to consciously limit the type and amount of food ingested in an attempt to either lose weight or prevent weight gain. In the short term, increasing CDR is a predictor of weight loss success¹. However, in the longer term, the maintenance of high CDR levels is challenging and adverse effects associated with CDR have been reported such as an increased risk of binge eating episodes².Moreover, some studies have shown that people with a high CDR when starting a weight loss diet have poorer outcomes, since the capacity to further increase their CDR is limited. For these subjects, weight loss interventions not relying on CDR increase are needed. In that regard, positive dietary approaches focusing on the inclusion of low energy density foods such as fruits and vegetables could be considered. Therefore, the aim of our study was to compare the effects on body weight and eating behaviors between a dietary intervention avoiding restrictive messages. The approach was one of emphasizing messages directed towards an increased consumption of fruits and vegetables (HIFV) and a traditional approach with a focus on restrictive messages to limit the consumption of high-fat foods (LOFAT).

Study design

As described in detail in previous publications from our group^3-5, sixty-eight postmenopausal women with abdominal obesity were randomly assigned to one of the two six-month dietary interventions (HIFV or LOFAT) that included three group sessions and ten individual sessions with a dietitian. The HIFV intervention focused on positive messages promoting the consumption of fruits and vegetables. The LOFAT approach focused on restrictive messages about decreasing high fat food consumption in the diet. Body weight was measured before and after the six-month intervention. CDR was measured before and after the intervention with the Three-Factor-Eating-Questionnaire which assesses three factors that refer to cognitions and behaviors associated with eating⁶. Besides the measurement of CDR, disinhibition (overconsumption of food in response to a variety of stimuli associated with a loss of control on food intake) and hunger (food intake in response to feelings and perceptions of hunger) were also measured.

Body weight decreases in response to the HIFV intervention

Body weight was significantly lower at the end of the six-month intervention compared to baseline in the LOFAT group (-3.5 ± 2.9 kg) as well as in the HIFV group (-1.6 ± 2.9 kg). The LOFAT group lost significantly more weight during the intervention than the HIFV group.

Cognitive dietary restraint is not a predictor of success in the HIFV intervention

CDR increased significantly in the LOFAT group during the intervention whereas no significant change was observed in the HIFV group. A large increase in CDR was associated with larger weight losses in the LOFAT group while in the HIFV group; changes in CDR were not associated with changes in body weight, suggesting that the HIFV approach was not relying on an increase in CDR to obtain a successful weight loss. Moreover, in the LOFAT group, women with higher baseline CDR had smaller weight loss in response to the intervention, which has also been reported by others^1;7. On the other hand in the HIFV group, no association was found between baseline CDR and change in body weight, meaning that a high CDR level at baseline was not a barrier to success when following the HIFV intervention.

Disinhibition and internal hunger decreased significantly in the HIFV group while no such changes were observed in the LOFAT group. In the HIFV group, the total weight of food consumed increased in response to the intervention and this could partly explain the decrease in internal hunger observed.

Conclusion

Following our HIFV intervention, we showed that weight loss could be achieved without increasing CDR. It could thus be argued that it is possible to lose weight without using CDR to control food intake. Therefore, our HIFV approach could be an alternative approach for women with high CDR as the success of the intervention does not rely on an increase in CDR as it is usually the case in traditional weight loss interventions such as our LOFAT approach.