The timing of meals

In most individuals, food intake occurs as discrete bouts or meals, and little attention has been paid to the factors that normally determine when meals will occur when food is freely available. On the basis of experiments using rats, the authors suggest that when there are no constraints on obtaining food and few competing activities, 3 levels of interacting controls normally dictate when meals will start. The first is the genetically determined circadian activity pattern on which nocturnal animals tend to initiate most meals in the dark. The second is the regularly occurring changing of the light cycle: These changes provide temporal anchors. The third relates to the size of the preceding meal, such that larger meals cause a longer delay until the onset of the next meal. Superimposed on these 3 are factors related to learning, convenience, and opportunity

Metabolic Effects of Bariatric Surgery in Mouse Models of Circadian Disruption

Background/Objectives: Mounting evidence supports a link between circadian disruption and metabolic disease. Humans with circadian disruption (for example, night-shift workers) have an increased risk of obesity and cardiometabolic diseases compared with the non-disrupted population. However, it is unclear whether the obesity and obesity-related disorders associated with circadian disruption respond to therapeutic treatments as well as individuals with other types of obesity. Subjects/Methods: Here, we test the effectiveness of the commonly used bariatric surgical procedure, Vertical Sleeve Gastrectomy (VSG), in mouse models of genetic and environmental circadian disruption. Results: VSG led to a reduction in body weight and fat mass in both ClockΔ19 mutant and constant-light mouse models (PP\u3e0.05). Within circadian-disrupted models, VSG also led to improved glucose tolerance and lipid handling (P\u3c0.05). Conclusions: Together these data demonstrate that VSG is an effective treatment for the obesity associated with circadian disruption, and that the potent effects of bariatric surgery are orthogonal to circadian biology. However, as the effects of bariatric surgery are independent of circadian disruption, VSG cannot be considered a cure for circadian disruption. These data have important implications for circadian-disrupted obese patients. Moreover, these results reveal new information about the metabolic pathways governing the effects of bariatric surgery as well as of circadian disruption

Central insulin and macronutrient intake in the rat

When rats are maintained on a standard laboratory diet, the infusion of low doses of insulin into the cerebroventricular system causes a reduction of food intake and body weight. It was recently reported that, if rats are maintained on a high-fat diet (56% calories as fat), they are insensitive to this action of insulin. To investigate further the effect of dietary composition on responsiveness to central insulin, we carried out two experiments. In experiment 1, rats were maintained on one of four equicaloric diets (providing 7, 22, 39, or 54% of calories as fat) before and during a 6-day third-ventricular infusion (i3vt) of insulin (10 mU/day) or saline. Rats consuming 7 or 22% of calories as fat had a significant reduction of both food intake (-17.2 +/- 2.9 and -14.6 +/- 3.3 g, respectively) and body weight (-50 +/- 5 and -41 +/- 5 g, respectively) from baseline over the insulin-infusion period. Rats consuming 39 or 54% calories as fat did not reliably alter food intake (-4.0 +/- 3.9 and -1.9 +/- 3.7 g, respectively) or body weight (-10 +/- 6 and -6 +/- 4 g, respectively) in response to i3vt of insulin. In experiment 2, rats were offered a choice of three macronutrients (carbohydrates, fats, and proteins) in separate jars in their home cages. After they had adapted to the diets, they were infused i3vt with insulin or saline. Insulin caused a significant reduction of body weight relative to saline-infused controls (body wt: -23.1 +/- 4 g) and a reduction in food intake that was selective for dietary fat. These data suggest that the effects of central insulin administration are highly dependent on the macronutrient content of the diet as well as the ability of rats to select their own diets

The brain is getting ready for dinner

Every evening, as we get ready for dinner, in addition to the routine behaviors of preparing the meal itself, we also prepare our bodies to cope with the upcoming meal. This could take the form of making restaurant reservations, changing into appropriate attire, washing hands, priming ourselves with an aperitif, or even consciously avoiding snacks as the meal approaches. A study by Johnstone and colleagues in this issue of Cell Metabolism (Johnstone et al., 2006) provides evidence that in parallel to our learned preparatory behaviors, our central nervous system is going through comparable motions as it gets ready for the anticipated meal

Comorbidity and Quality of Life in Adults with Hair Pulling Disorder

Hair pulling disorder (HPD; trichotillomania) is thought to be associated with significant psychiatric comorbidity and functional impairment. However, few methodologically rigorous studies of HPD have been conducted, rendering such conclusions tenuous. The following study examined comorbidity and psychosocial functioning in a well-characterized sample of adults with HPD (N=85) who met DSM-IV criteria, had at least moderate hair pulling severity, and participated in a clinical trial. Results revealed that 38.8% of individuals with HPD had another current psychiatric diagnosis and 78.8% had another lifetime (present and/or past) psychiatric diagnosis. Specifically, HPD showed substantial overlap with depressive, anxiety, addictive, and other body-focused repetitive behavior disorders. The relationships between certain comorbidity patterns, hair pulling severity, current mood and anxiety symptoms, and quality of life were also examined. Results showed that current depressive symptoms were the only predictor of quality of life deficits. Implications of these findings for the conceptualization and treatment of HPD are discussed

Clarifying the Relationship Between Trichotillomania and Anxiety

Although research has consistently linked unidimensional anxiety with Trichotillomania (TTM) severity, the relationships between TTM severity and anxiety dimensions (e.g., cognitive and somatic anxiety) are unknown. This knowledge gap limits current TTM conceptualization and treatment. The present study examined these relationships with data collected from ninety-one adults who participated in a randomized clinical trial for TTM treatment. Based on prior research, it was hypothesized that TTM severity would be related to the cognitive anxiety dimension and that psychological inflexibility would mediate the association. Hypotheses were not made regarding the relationship between TTM severity and somatic anxiety. Regression analyses indicated that only cognitive dimensions of anxiety predicted TTM severity and that psychological inflexibility mediated this relationship. Implications for the conceptualization and treatment of TTM are discussed