اثر القای خلق بر روی رفتار غذایی و ولع مصرف سیگار در رژیم غذایی

Women high in dietary restraint (“restrainers”) increase food intake more than nonrestrainers following emotional arousal. When restrained smokers are deprived of cigarettes during elevated mood states, nicotine craving should increase with food craving. The present study investigated the interaction of smoking and affect on food intake in 60 women, 18–25 years old, who were identified as restrainers. The study consisted of smokers and nonsmokers who viewed a domestic violence or comedy film segment, followed by exposure to snacks. Emotional arousal, regardless of valence, did not result in a difference in food consumption between smokers and nonsmokers. Furthermore, smokers showed similar levels of nicotine craving after both films. Self-report of mood changed only in the domestic violence condition, indicating the difficulty of positive mood induction. Limitations to the study and suggestions for further research are discussed.

Restrained eaters typically restrict food intake to lose or maintain body weight. They employ cognitive control over physiological hunger (Herman & Polivy, 1984). In situations where their self-control is hindered, such as during stress, restrainers may violate their dieting practices and overeat. Such disinhibited eating is more common in women than men (Grunberg & Straub, 1992). Those individuals who are not restrained eaters typically decrease food intake when under stress (Herman & Polivy, 1975). Restrained women are also more likely than their unrestrained counterparts to substitute eating with other methods of regulating hunger and weight, including cigarette smoking. In fact, the smoking rates among women who diet are two times higher than among nondieters (Krahn, Kurth, Demitrack, & Drewnowski, 1992). 1.1. Emotional arousal and eating behavior Several studies have examined the effects of negative emotional arousal, including anxiety, stress, and depression, on eating behavior. For purposes of this paper, the terms “emotional arousal,” “mood,” and “affect” are used interchangeably. Herman and Polivy (1975) demonstrated that anxiety caused by anticipated electrical stimulation increased intake of ice cream in restrainers, with the opposite effect in nonrestrainers. Similarly, Rutledge and Linden (1998) found that following stress-inducing laboratory cognitive tasks (mental arithmetic, Stroop, and word scramble), restrained eaters increased their consumption of snacks (chocolate chip cookies and crackers), whereas nonrestrained eaters decreased their consumption. Physiological measures of blood pressure and heart rate were used to corroborate self-reported levels of stress. Schotte, Cools, and McNally (1990) presented a 20-min segment from a frightening film to induce anxiety, sadness, and anger, which triggered overeating of popcorn in restrained eaters. In general, studies on positive emotions are less common than those on negative emotions. The effect of positive emotional arousal on eating behavior has been examined in only one prior study. Cools, Schotte, and McNally (1992) repeated the mood induction design of Schotte et al. (1990), but added a 20-min comedy film segment to induce positive affect. They found that positive affect results in a similar, but not as extreme, increase in food intake among restrainers. Thus, the disinhibiting effects of mood on food intake in restrainers are not limited to negatively valenced affective states. Further research is needed, however, to show whether the intensity of the induced emotions has a greater impact than valence. 1.2. Cigarette smoking, emotional arousal, and eating behavior Smokers who experience negative emotional arousal tend to use cigarettes to enhance mood (Pomerleau & Pomerleau, 1987). During smoking abstinence, smokers report an increase in nicotine craving (Borelli, Bock, King, Pinot, & Marcus, 1996). When smokers high in dietary restraint are deprived of cigarettes during negative mood states, nicotine craving should increase with food craving. Thus, smoking abstinence and negative mood states may have an additive effect on food intake in restrained women. A study by Ogden (1994) suggests an association between smoking abstinence and the desire for food. Following 24 h of smoking abstinence, food intake among smokers was significantly correlated with dietary restraint. This effect was not observed among those smokers who did not abstain from smoking prior to the lab or among nonsmokers. The interaction of stress, smoking, and dietary restraint in women was first examined by Mitchell and Perkins (1998). As expected, food intake following a stressful computerized recall task decreased for nonrestrained nonsmokers but increased for restrained nonsmokers. However, among smokers, food intake decreased in restrainers and increased in nonrestrainers. The results of this study deviate from prior mood induction research with restrained eaters. There are several possible explanations for this unexpected finding. The sample induced women ranging in age from 18 to 40, which differs from samples of prior eating restraint studies that use a narrower age range. Also, physiological measures were not included to substantiate self-reported stress levels. The inclusion of reliable physiological measures, such as blood pressure, allows researchers to better quantify and examine levels of stress (Rutledge & Linden, 1998). Thus far, no studies have evaluated the interaction of smoking and eating behavior following positive emotional arousal. 1.3. Physiological mechanisms Most researchers agree that food cravings are the result of a physiological event. The serotonergic theory suggests that people crave carbohydrates when their brains are low in serotonin, a neurotransmitter responsible for reducing appetite, alleviating irritability, and elevating moods (Wurtman & Wurtman, 1989). Carbohydrate foods act through the hormone insulin to stimulate brain tryptophan levels and convert these levels to serotonin. People feel depressed, irritable, or tense when serotonin levels are low, whereas eating carbohydrates indirectly raises serotonin levels in the brain, creating a euphoric effect (Fernstrom & Wurtman, 1971). In women who restrict carbohydrates in their diet, serotonin is especially low. The induction of a negative emotion, like stress, will only further increase the need for serotonin, making the brain even more “hungry” for carbohydrates. Nicotine also increases serotonin, as evidenced by several studies in which subjects report a decrease in subjective distress following smoking Gilbert et al., 1989, Pomerleau & Pomerleau, 1987 and Pomerleau et al., 1984. Therefore, since nicotine functions like carbohydrates, women who smoke cigarettes and are high in dietary restraint use nicotine to compensate for the deficit of carbohydrates in their diet (Ogden, 1994). When these women abstain from smoking, such as in a lab setting, they experience nicotine withdrawal, which then decreases serotonin. This results not only in an increased craving for nicotine, but also in an increased craving for sweets and in elevations in anxiety, irritability, and depression. Thus, when women quit smoking, those high in dietary restraint are likely to eat more, and subsequently gain more weight, than those low in dietary restraint. 1.4. Psychological mechanisms Several psychological theories have been suggested to explain the enhanced eating of distressed restrainers. First, according to the psychosomatic approach, eating may provide at least temporary comfort or relief from anxiety for these individuals (Herman & Polivy, 1975). Herman and Polivy (1988) posit that overeating serves as a distraction from one's worries. Rather than dwelling on the actual stressor, the chronic dieter turns to food and misattributes the distress to the overeating itself. For restrainers, the distress over breaking one's diet is more familiar and easier to deal with than the distress arising from more serious threats to emotional well-being. This functional explanation predicts a short-term reduction in anxiety as a result of overeating. The boundary model (Herman & Polivy, 1984) states that any intense stimulus that disrupts the cognitive control processes of restrainers will result in overeating. By definition, restrained eaters control eating through high levels of self-awareness of their standards of consumption (i.e., their diet), as well as through careful monitoring of food intake. According to this view, when restrainers cease to be self-aware or when they fail to monitor intake, disinhibited eating is likely to occur. A stressful situation is one type of condition that may interfere with self-regulation. Application of a reinforcement model has also been suggested as a psychological mechanism for overeating. The reinforcing value of any reinforcer can be defined as the degree to which an individual will work to obtain it (Woolverton & Nader, 1992). An increase in food intake for restrainers is common following smoking cessation, which can be viewed as the removal of nicotine, a highly powerful reinforcer. That is, food gains reinforcing value when cigarettes are deprived. In addition, eating declines after smoking resumption since food loses reinforcing value when the strong reinforcer of nicotine returns (Perkins, 1992). 1.5. Summary and hypotheses Negative emotional arousal plays a significant role in both overeating and smoking. When women who restrain their diet are distressed, they typically eat more. Psychologically and physiologically, food intake is associated with decreased negative mood. An increase in negative affect also predicts smoking behavior since nicotine has been shown to have a mood-enhancing effect. In addition, nicotine withdrawal leads to depression, anxiety, and increased cigarette craving (Borelli et al., 1996). Thus, women who are both dietary restrainers and cigarette smokers attempting to quit may be more likely to overeat and to crave cigarettes following negative effect. Since food and cigarettes both act to increase positive moods through mental and physical mechanisms, negative arousal only further inhibits the control over disinhibited eating and nicotine craving. It has yet to be determined whether positive emotional arousal also predicts these two behaviors in restrained eaters who smoke. The present study was designed to measure the interaction of smoking status (smokers vs. nonsmokers) and emotional arousal (positive vs. negative) on food intake in restrained women. We included only women since dietary restraint is much more common in this population. Furthermore, since most previous research has shown that an increase in food intake following positive or negative emotional arousal occurs only in restrained eaters, we limited our sample to women with high scores on the Restraint Scale (Herman & Polivy, 1980). Our purpose was to improve upon the design of Mitchell and Perkins (1998) by adding physiological measures to confirm self-reported levels of induced emotional arousal. We also reexamined their unusual finding that restrained abstinent smokers will eat less than restrained nonsmokers following a stressful task. In addition, we replicated Cools et al.'s (1992) design that used comedy and horror films to test the effects of both positive and negative mood induction, respectively, on food intake. Since films typically induce a variety of affect changes, mood was assessed on both positive and negative dimensions for each film. We did not expect that the difference in food consumption between smokers and nonsmokers would depend on the type of film viewed. Rather, we expected that smoking alone would account for differences in food intake, regardless of film condition. We hypothesized that smokers would eat more than nonsmokers following a negative emotionally arousing film segment. After a positive emotionally arousing film segment, we also expected greater food intake among smokers because, in contrast to Cools' mood induction procedure, we used film segments that were more relevant to women. Finally, among abstinent smokers, we predicted that food intake in both film conditions would be positively correlated with self-reported nicotine craving. In other words, since participants were deprived of cigarettes in the laboratory, their consumption of available snack foods should increase as their nicotine craving increases. Thus, it was anticipated that arousal, regardless of valence, would impact on both eating behavior and nicotine craving.