Biological determinants of spontaneous physical activity

Variation and homogeneity in affective responses to physical activity of varying intensities: an alternative perspective on dose-response based on evolutionary considerations

A model for systematic changes in patterns of inter-individual variation in affective responses to physical activity of varying intensities is presented, as a conceptual alternative to the search for a global dose-response curve. It is theorized that trends towards universality will emerge in response to activities that are either generally adaptive, such as moderate walking, or generally maladaptive, such as strenuous running that requires anaerobic metabolism and precludes the maintenance of a physiological steady state. At the former intensity the dominant response will be pleasure, whereas at the latter intensity the dominant response will be displeasure. In contrast, affective responses will be highly variable, involving pleasure or displeasure, when the intensity of physical activity approximates the transition from aerobic to anaerobic metabolism, since activity performed at this intensity entails a trade-off between benefits and risks. Preliminary evidence in support of this model is presented, based on a reanalysis of data from a series of studies.

Atypical antipsychotic weight gain: a major clinical challenge

OBJECTIVE

The major aim of this paper is to review findings from weight management intervention studies to consider clozapine and/or olanzapine induced weight gain. A parallel aim is to summarize the challenges facing future research and provide an overview of best practice in the management of weight in mental health patients.

METHOD

A systematic literature search was conducted using Medline, Cinahl and PsychINFO data bases and reference lists from relevant published articles. Five studies which reported weight control practices in patients taking atypical antipsychotic medications were located and reviewed.

RESULTS

The studies reviewed provide some important descriptive clinical insights; however, common shortcomings include small subject numbers and methodological drawbacks such as lack of a control group.

CONCLUSIONS

There is some evidence that weight gain associated with atypical antipsychotic medication can be ameliorated by lifestyle changes such as improved nutritional practices and increased physical activity. Lifestyle interventions for individuals with psychotic disorders may need to be adapted to be most effective; for example, using strategies to counter increased appetite and to enhance physical activity. Clinicians need to be vigilant and persistent in monitoring and intervening if weight gain occurs. A standardized screening tool and clinical pathway would help clinicians to target appropriate interventions for each person prescribed atypical antipsychotic medication.

Genetic contributions to body weight in mice: relationship of exploratory behavior to weight

OBJECTIVE

The A/J and C57BL/6J mouse strains differ markedly in their exploratory behavior and their weight gain on a high-fat diet. We examined the genetic contributions of exploratory behavior to body weight and tested for shared, pleiotropic loci influencing energy homeostasis.

RESEARCH METHODS AND PROCEDURES

Segregating (AxB6)F2 intercross (n = 514) and (B6AF1xA/J)N2 backcross (N = 223) populations were studied, phenotyping for weight and exploratory behaviors. Relationships among traits were analyzed by correlations. Weight traits were dissected with a genome-wide scan.

RESULTS

Modest correlations were found between exploratory behaviors and weight, explaining 2% to 14% of the variance. Quantitative trait loci (QTL) for body weight at 8 weeks (wgt8), 10 weeks (wgt10), and 2-week weight gain (difference between weeks 8 and 10) on a 6% fat diet were mapped. Two QTL on chromosome 1 (peaks at 66 cM and 100 cM; Bw8q1) affected wgt8 [likelihood of the odds ratio (Lod), 3.0 and 4.4] and wgt10 (Lod, 2.2 and 3.4), respectively. In the backcross, a significant QTL on chromosome 4 (peak at 66 cM; Bw8q2) affected wgt 8 (Lod, 3.3) and wgt10 (Lod, 3.1). For 2-week weight gain, suggestive QTL were mapped on chromosomes 4 and 6. The chromosome 6 QTL region overlaps a human 7q locus for obesity. A search for between-strain sequence polymorphisms in the leptin and NPY genes was unrevealing.

DISCUSSION

In mice, loci influencing exploratory activity play a modest role in body-weight regulation. Some forms of obesity may emerge from loci regulating normal body weight.