دریافت انرژی و ریزمغذی در بولیمیا

Energy deprivation and malnutrition are often thought to be key factors in the maintenance of bulimia nervosa (BN). Our review shows that it is unclear how much energy is actually available to BN patients' metabolism because the contribution of food consumed during binge eating is generally neglected. Also, there is little evidence for another key hypothesis that binge-eating episodes are triggered by carbohydrate craving. This study examined energy consumption and macronutrient composition of meals and binge-eating episodes in food diaries. Forty female BN patients, 40 female panic disorder (PD) patients, and 40 healthy women recorded their food intake while in their natural environment during two consecutive days. We did not find the expected evidence for chronic energy deprivation and malnutrition in BN patients. Also, there was no evidence that carbohydrate craving drives binge eating. The implications for models of BN and for treatments targeting eating behavior are discussed.

Energy deprivation and malnutrition due to abnormal nutrient composition of meals are often thought to be involved in maintaining bulimia nervosa (BN). Several theorists propose that excessive dieting can lead to energy deprivation with severe biological consequences which are assumed to be relevant for the etiology and maintenance of bulimia Booth et al., 1990, Fairburn & Cooper, 1989 and Orleans & Barnett, 1984. Indeed, observed meals consumed in the laboratory which were not labeled as binge-eating episodes were smaller than typical meals of normal people Mitchell & Laine, 1985 and Rosen et al., 1985. Outside of the laboratory, BN patients report to be fasting between the binge-eating episodes Pyle et al., 1981, Weiss & Ebert, 1983 and Woell et al., 1989. BN patients consume fewer calories than controls in regular meals and snacks (Davis, Freeman, & Garner, 1988) and on days when no binge-eating episodes occur, BN patients consume fewer calories than normal controls (Schweiger, Laessle, Fichter, & Pirke, 1988), but this was not always found either (van der Ster Wallin, Norring, Lennernas, & Holmgren, 1995). A more direct link between energy deprivation and binge eating comes from a study where fewer calories were counted in the food diaries before the onset of a binge episode than controls consumed up to the same time of day (Davis et al., 1988), but this was not always found (Lingswiler, Crowther, & Stephens, 1989). Whereas total energy consumption, including binge eating, did not differ between BN patients and healthy controls in one study (Gleaves, Williamson, & Barker, 1993), it was much higher in BN patients than in controls in another study (Gendall, Sullivan, Joyce, Carter, & Bulik, 1997), but, this may have been an overestimation of energy that was actually available for metabolism because the loss of calories due to purging was not taken into account. It is therefore necessary to examine the contribution binge-eating episodes make to the actual energy intake. Estimates of calories consumed during binge eating from patient's memory recall are between 3500 and 5000 kcal Johnson et al., 1982 and Mitchell et al., 1981. When patients were instructed to eat as much as possible in the laboratory, the consumption was in the same range of between 3300 and 4500 kcal Hadigan et al., 1989, Hadigan et al., 1992, Kaye et al., 1986, Kaye et al., 1992, Mitchell & Laine, 1985, Walsh et al., 1992, Walsh et al., 1989 and Walsh et al., 1989. However, this is much more than what was found in food protocols outside of the laboratory where binges contained between 1100 and 1500 kcal Davis et al., 1988, Elmore & deCastro, 1991, Gendall et al., 1997, Gleaves et al., 1993, Rosen et al., 1986, Rossiter & Agras, 1990 and Rossiter et al., 1988. Aside from these discrepancies, none of the studies we reviewed estimated the energy that is actually retained after purging. In addition to energy deprivation, chronic malnutrition has been proposed to be a maintaining factor of BN. The total consumption in BN patients (i.e., nonbinge meals plus binge-eating episodes) had a lower carbohydrate and protein content compared with healthy controls (Woell et al., 1989), but a higher proportion of protein was found in another study (Blouin et al., 1993) and in a laboratory study where BN patients consumed food items with less fat than the control group (Walsh, Kissileff, Cassidy, et al., 1989). Looking at meals from nonbinge days only, the proportion of protein was higher, while that of carbohydrates was lower, in BN patients compared to controls (Schweiger et al., 1988), which is a pattern also found in laboratory meals Gwirtsman et al., 1989 and Walsh et al., 1989. In addition to the compensation for malnutrition, the craving for specific macronutrients contained in food consumed during bingeing was suggested as a driving force of binge eating because carbohydrates may have a mood-lifting effect (Wurtman, 1988). Because a number of patients stated in interviews that they consumed mostly carbohydrate-rich food when binge eating (Abraham & Beumont, 1982), “carbohydrate craving” has been frequently described as one of the key features of binge eating although there is little evidence supporting it. The relative contribution of carbohydrates to the energy consumed is not higher in food consumed during binge-eating episodes than in normal meals consumed by healthy people Kaye et al., 1992, Walsh et al., 1987, Walsh et al., 1989 and Walsh et al., 1989 and not different from nonbinge meals of BN patients Gendall et al., 1997, Jansen et al., 1989, Rosen et al., 1986, Walsh et al., 1992, Walsh et al., 1989 and Walsh et al., 1989. However, the fat content is higher in binge-eating episodes of BN patients than in controls' meals Kaye et al., 1992 and Woell et al., 1989 and in patients' nonbinge meals in two studies Gendall et al., 1997 and Walsh et al., 1989, but not in another study (Walsh, Kissileff, Cassidy, et al., 1989). Protein was found to contribute less to the energy consumed in binges than in meals of controls (Walsh et al., 1992) and in patients' nonbinge meals Gendall et al., 1997, Rossiter et al., 1990, Walsh et al., 1989 and Walsh et al., 1989. The first goal of this study was to examine the energy consumption during nonbinge meals and binge-eating episodes separately. We also estimated the actual energy intake taking into account that even when purging occurs, binge eating contributes to the energy available to the body. A second goal was to assess the macronutrient composition of meals and examine whether they provide evidence for malnutrition in BN patients. A third goal was to examine whether the macronutrient composition of binge-eating episodes is characterized by a larger proportion of carbohydrates. We tested these questions in a group of BN inpatients and outpatients. To determine whether certain eating behaviors are specific to BN or are generally associated with psychopathology, a group of patients with panic disorder (PD) were tested in addition to healthy controls. Study participants were asked to continuously record their food intake in their natural environment.