To our knowledge, this is one of the first studies evaluating the effects of informing obese people about the possible genetic origin of their being overweight, and it was unclear whether this information is helpful or harmful. In familial hypercholesterolemia, it was found that information about genetic backgrounds can reduce the beliefs that diets might be helpful.7
The results of our study show that obese people highly appreciate a general consultation, and the additional inclusion of genetic information can lead to new insights about weight problem. This suggests that genetic information about obesity is well-received. It was previously hypothesized that genetic testing and information about obesity may motivate healthier behavior,15
although others reject this idea.16
The results do not show any evidence for negative effects of genetic information on the eating behavior or self-control of obese people. Self-efficacy was comparable between different intervention groups and remained stable at the 6-month follow-up. This is very important, as self-motivation is one of the few predictors of weight control in obesity.17
Restraint eating increased at follow-up, but did not differ between groups. Weight was not substantially influenced by the interventions.
Another hypothesis was that personal relevance of genetic information might moderate the effects of the intervention. This was confirmed for the variable “negative affect”. The consultations led to substantial short-term decreases in negative affect, which relapsed partially at follow-up. However, this effect was moderated by family history of obesity (parents, brothers or sisters are also obese) and intervention type. If participants had a family history of obesity and received consultations including genetic information, this resulted in less negative mood at follow-up than before the intervention; the same was true for those participants without a family history of obesity who received a consultation without genetic information. Thus, depending on the personal relevance, the consultation should include genetic information or not. If the consultation matches the needs of the participants, it results in small, but positive long-term effects in terms of reduced negative affectivity.
There were no negative effects of the interventions on body weight. The only effect on body weight was for family history of obesity. Participants without a family history reported somewhat lower body weights at 6 months follow-up. Although this might be related to easier weight reduction in participants without family determinants of obesity, these data should not be overinterpreted. The weight data at follow-up were self-reported and might be subject to different distortions.
A criticism of these results could be that the effects are weak and that a correction of alpha inflation would abolish most described effects. However, with a 1-session consultation lasting 30 to 40 minutes, stronger effects cannot be expected and alpha correction would lead to a nondetection of possible weak or moderate effects. As possible negative effects were also tested, it would be more harmful not to detect them than accepting some alpha error inflation. We also did not report the intend-to-treat analyses, as they confirm the significance of results whereas reducing effect sizes; thus, not changing the pattern of results. Furthermore, the sample was informed that genetic tests would be done because of an associated study, which might have led to a selection bias, favoring the inclusion of people with positive attitudes toward genetics. This information had to be provided for ethical reasons; and therefore, this selection bias was unavoidable. To know more about generalizability, the study should be replicated without genetic tests and with other samples than GP patients. Finally, the interventions differed in duration with the genetic consultation lasting about 10 minutes longer; however, as the whole assessment took about 1 1/2 hours, it is unlikely that this time difference explains the effects. These shortcomings point to the fact that further replication is warranted.
These results have direct implications for clinical work. Considering the failure or weak effects of nonsurgical interventions in obesity,18–20
providing realistic information to affected people is crucial. Responding to the global epidemic of obesity, consultation is the major ingredient of a stepped care decision.19
Many obese people appreciate receiving information about realistic goals for weight change, about normalizing eating behavior, and increasing physical activity. If obese people have signs of genetic risk (e.g., MC4R mutations or family history of obesity), the consultation should include information about the genetic transmission of obesity. A summary of topics for consultation, which were appreciated from our obese patients is presented in Table .