Food Deprivation

Abstract

Food deprivation, which MeSH classifies under motivation, is the withholding or restriction of food, from an overnight fast to the semistarvation of the Minnesota experiment. This article covers how deprivation has been used to manipulate motivation in the laboratory, how fasting raises the reward value of food and draws attention to food cues, what short-term fasting and intermittent fasting do to cognition and mood, and how restriction relates to binge eating and to heightened drug reward. The central question is how much deprivation changes the mind beyond appetite: in the studies cited here its effects on food reward are consistent, but its effects on general cognition are not.

Keywords: food deprivation, fasting, food restriction, food reward

Deprivation is one of the oldest tools of motivation research. Nutritional state, fasted or fed, is recognized to change activity in brain reward systems (Goldstone et al., 2009), and fasting has served as a comparison for social isolation, which causes social craving similar to the way fasting causes hunger (Tomova et al., 2020).

What Food Deprivation Is

Food deprivation ranges from hours to months. Intermittent fasting, for instance, is defined as the abstinence or strong limitation of calories for 12 to 48 hours, alternated with periods of regular food intake (Gudden et al., 2021). At the other extreme, during World War II 36 conscientious objectors took part in the Minnesota Starvation Experiment, conducted by Ancel Keys and colleagues to study the physical and psychological effects of semistarvation and the problem of refeeding; most lost more than 25% of their weight, and many experienced anemia, fatigue, apathy, extreme weakness, irritability, neurological deficits and lower extremity edema (Kalm & Semba, 2005). The experiment's primary report was published as The Biology of Human Starvation (Keys et al., 1950).

Restriction has psychological costs. A review of food restriction concluded that starvation and self-imposed dieting appear to result in eating binges once food is available, and in preoccupation with food and eating, increased emotional responsiveness and dysphoria, and distractibility (Polivy, 1996).

MeSH files food deprivation as a narrower descriptor of motivation and lists no narrower descriptors beneath it.

Deprivation as a Motivational Manipulation

Learning research has long varied deprivation to vary motivation. One classic study examined the effect of deprivation and frequency of reinforcement on variable-interval responding (Clark, 1958). Yet deprivation is not necessary for eating: after Pavlovian conditioning, presentation of a cue associated with food elicited feeding in sated rats (Weingarten, 1983).

Deprivation was also set against other influences on eating: one study compared the effects of fear, food deprivation and obesity on eating (Schachter et al., 1968).

Deprivation also has a neural signature. Starvation-sensitive AGRP neurons in mice exhibit properties consistent with a negative-valence teaching signal: mice avoided their activation, and their activity rapidly fell in response to food-related cues (Betley et al., 2015). The sensory detection of food is sufficient to rapidly reverse the activation of these neurons induced by energy deficit, before any food is consumed (Chen et al., 2015). A rival finding is that brief stimulation of AgRP neurons before food was available promoted intense appetitive and consummatory behavior for tens of minutes through a long-lasting potentiation of the rewarding properties of food (Chen et al., 2016). A review of motivation concepts notes that motivation was once thought of in terms of aversive drives and reward in terms of drive reduction, that drive concepts were largely replaced by incentive concepts in which hunger acts to enhance the incentive value of food, and that the finding that mice will work to turn on these neurons makes a pure drive reduction theory of AgRP hunger less plausible (Berridge, 2018).

Deprivation reorders other motives. Using hypothalamic AgRP neurons as an entry point, hunger significantly increased its capacity to suppress competing motivational systems such as thirst, anxiety-related behavior, innate fear and social interaction, often only when food was accessible (Burnett et al., 2016).

Reward and Attention

Deprivation raises the value of food. In 20 non-obese adults scanned once after breakfast and once after an overnight fast, fasting selectively increased activation to pictures of high-calorie over low-calorie foods in the ventral striatum, amygdala, anterior insula and orbitofrontal cortex, and enhanced the subjective appeal of high-calorie foods (Goldstone et al., 2009). In hungry or satiated women, food deprivation increased activity following the presentation of high-calorie foods, although the initially applied test found no effect of food deprivation in the amygdala or OFC and the effect appeared in a less strict conjunction analysis; amygdala and medial orbitofrontal activity appeared only when participants explicitly evaluated the foods (Siep et al., 2009). After a 24-hour fast, appetite scores, hedonic 'liking' ratings and buffet energy intake increased, the relative reinforcing value of snack foods increased, and explicit 'wanting' increased for all food categories (Cameron et al., 2014).

Deprivation also directs attention. In a dot probe task, people with high levels of hunger showed a greater attentional bias for food-related words shown for 500 ms than people with low hunger, with no evidence of a hunger-related bias when words were shown for 14 ms and masked, suggesting that a non-emotional motivational state is associated with a bias in selective attention for stimuli relevant to that state (Mogg et al., 1998). After 10 hours of fasting, midbrain regions showed selective activation to food cues, and across deprivation sessions deprivation narrowed and focused the brain's motivational responses to the deprived target (Tomova et al., 2020).

Figure 1

Length of Food Deprivation in Four Studies and a Definition of Intermittent Fasting

Cognition and Mood

The effects of short-term fasting on general cognition are inconsistent. A systematic review of ten studies in healthy people, which excluded attentional bias to food-related stimuli, found equivocal results: several studies reported no observable differences as a result of fasting and others showed specific deficits on tasks of psychomotor speed, executive function and mental rotation (Benau et al., 2014). A review of intermittent fasting likewise found no clear evidence of a positive short-term effect on cognition in healthy subjects (Gudden et al., 2021). Severe combined stressors are another matter: during a 53-hour military exercise combining sleep loss, heat, dehydration and undernutrition, vigilance, reaction time, attention, memory and reasoning were impaired and mood deteriorated (Lieberman et al., 2005).

Hunger also colors emotion. In a 21-day experience sampling study of 64 people, greater self-reported hunger was associated with greater anger and irritability and lower pleasure, whereas associations with arousal were not significant (Swami et al., 2022). One account holds that hunger alone is insufficient for feeling 'hangry': in three studies, hunger shifted affective perceptions in negative but not neutral or positive contexts, and caused negative emotions and negative judgments of a researcher only when participants were not aware that they were conceptualizing their affective state as emotion (MacCormack & Lindquist, 2019).

Restriction, Bingeing and Drug Reward

Restriction can outlast itself. In rats subjected to 12-week cycles of restriction and refeeding, those with a history of restriction and hyperphagia continued to binge, especially on palatable food, 30 days after full feeding was restored; the authors note that the Minnesota experiment and studies of prisoners of war show that chronic restriction produces changes in eating behavior, including binge eating, that endure decades after restriction has ceased (Hagan & Moss, 1997).

Restraint theory supplied the human hypothesis. Separating normal-weight people into hypothetically deprived high-restraint and non-deprived low-restraint groups, one study found that high-restraint subjects' intake varied directly with preload size whereas low-restraint subjects ate in inverse proportion to it, and proposed restraint as an important behavioral mechanism affecting the expression of hunger (Herman & Mack, 1975); dieting and binging were later given a causal analysis (Polivy & Herman, 1985).

Whether dieting causes binge eating in people is disputed. Although it is widely accepted that dieting increases the risk for bulimic pathology, a randomized experiment that assigned 82 nonobese women to a 6-week low-calorie diet or a waitlist control found that, contrary to the restraint model, dieting resulted in significant decreases in bulimic symptoms relative to control; the authors concluded that dieting does not promote bulimic pathology (Presnell & Stice, 2003).

Restriction also changes other rewards. Chronic food restriction and low body weight have long been known to increase the self-administration of abused drugs, and in rats chronic food restriction augments the rewarding effect of diverse drugs of abuse, an effect attributed to increased sensitivity of a neural substrate rather than to a change in drug bioavailability (Carr, 2002). Unlike the persistent bingeing above, this augmentation abates within 1 week of restored ad libitum feeding and weight gain (Carr, 2002).

Worked Example

The Minnesota figures can be put in absolute terms. Most participants lost more than 25% of their weight (Kalm & Semba, 2005). For a man weighing 70 kg at the start, a 25% loss is 0.25 × 70 = 17.5 kg, leaving 52.5 kg; any loss beyond 25% takes him lower. By contrast, the fasted condition in one imaging study was 15.9 hours since supper, against 1.6 hours since breakfast in the fed condition (Goldstone et al., 2009), a difference of about 14.3 hours, under a single missed meal.

Discussion

Three conclusions follow for cognitive psychology. First, in the studies cited here, deprivation raised the value of food. Fasting increased brain responses to high-calorie foods (Goldstone et al., 2009) and increased 'wanting' and 'liking' (Cameron et al., 2014).

Second, its effects on general cognition are less reliable. Reviews of short-term and intermittent fasting find inconsistent or no clear effects in healthy people (Benau et al., 2014; Gudden et al., 2021), whereas hunger biases attention specifically toward food (Mogg et al., 1998).

Third, restriction can have lasting consequences. A history of restriction and refeeding produced persistent binge eating in rats (Hagan & Moss, 1997), and a review concluded that dieting appears to result in eating binges once food is available (Polivy, 1996), although a randomized diet trial in women decreased bulimic symptoms (Presnell & Stice, 2003).

Current Directions

Three lines of work are active. Intermittent fasting: a review reports clinical studies showing benefits of intermittent fasting for epilepsy, Alzheimer's disease and multiple sclerosis, some based on very small samples, and notes that longitudinal studies and randomized clinical trials will provide a window into long-term effects (Gudden et al., 2021). Everyday hunger: experience sampling links everyday hunger to anger, irritability and lower pleasure (Swami et al., 2022). Other needs: fasting has served as a comparison for social isolation, with midbrain regions showing selective activation to food cues after fasting and to social cues after isolation (Tomova et al., 2020).

Common Misconceptions

“Skipping meals sharpens the mind.”

A review of intermittent fasting found no clear evidence of a positive short-term effect on cognition in healthy subjects (Gudden et al., 2021).

“Hunger always makes people irritable.”

In laboratory studies, hunger shifted affective perceptions in negative but not neutral or positive contexts (MacCormack & Lindquist, 2019).

“The effects of dieting end when the diet ends.”

Rats with a history of restriction and refeeding continued to binge 30 days after full feeding was restored (Hagan & Moss, 1997).

Glossary

AgRP neurons.

Starvation-sensitive hypothalamic neurons activated by energy deficit.

Attentional bias.

Selective attention to stimuli relevant to a current state, shown for food words in hunger.

Binge eating.

Episodes of excessive eating, reported after restriction once food is available.

Dot probe task.

A task used to measure selective attention to words or pictures, such as food-related words.

Experience sampling.

Repeated reports of states such as hunger and anger collected several times a day in daily life.

Fasting.

Going without food for a period, from an overnight fast to 24 hours or more in the studies cited here.

Food restriction.

Limiting food intake below what would otherwise be eaten, whether by dieting or by experimental design.

Hangry.

The colloquial notion that people become angry when hungry.

Intermittent fasting.

Abstinence or strong limitation of calories for 12 to 48 hours, alternated with periods of regular food intake.

Liking.

The hedonic evaluation of a food, which increased after a 24-hour fast.

Minnesota Starvation Experiment.

A World War II study of semistarvation and refeeding in 36 conscientious objectors.

Relative reinforcing value.

A measure of how hard a person will work for a food, which rose for snack foods after fasting.

Semistarvation.

Prolonged severe undernutrition, in which most Minnesota participants lost more than 25% of their weight.

Wanting.

The motivational value of a food, measured by responses to food images and by its relative reinforcing value.

Key Researchers

Kent C. Berridge

. Professor in the Department of Psychology at the University of Michigan; reviewed how drive concepts of motivation gave way to incentive concepts. ORCID - Wikipedia - Faculty Page

Brendan P. Bradley

. Psychologist at the University of Southampton; co-authored the study of selective attention to food-related stimuli in hunger. ORCID - Faculty Page - Google Scholar

Scott M. Sternson

. Neuroscientist at the University of California, San Diego and the Howard Hughes Medical Institute; co-authored the study of starvation-sensitive AGRP neurons as a negative-valence teaching signal. ORCID - Faculty Page

Frequently Asked Questions

What is food deprivation in psychology?

It is the withholding or restriction of food, studied from overnight fasts (Goldstone et al., 2009) to the semistarvation of the Minnesota experiment (Kalm & Semba, 2005).

What happened in the Minnesota Starvation Experiment?

Thirty-six conscientious objectors underwent semistarvation in which most lost more than 25% of their weight, and many experienced fatigue, apathy, irritability and neurological deficits (Kalm & Semba, 2005).

Does fasting make food more rewarding?

After a 24-hour fast, 'wanting' and 'liking' of food increased (Cameron et al., 2014), and an overnight fast increased brain responses to high-calorie foods (Goldstone et al., 2009).

Does hunger change what people notice?

People with high hunger showed a greater attentional bias toward food-related words than people with low hunger (Mogg et al., 1998).

Does fasting impair thinking?

A systematic review found equivocal results, with some studies showing no differences and others specific deficits in psychomotor speed, executive function and mental rotation (Benau et al., 2014).

Is being hangry real?

In daily life, greater hunger was associated with greater anger and irritability (Swami et al., 2022), and in the laboratory hunger shifted affective perceptions only in negative contexts (MacCormack & Lindquist, 2019).

Does dieting lead to binge eating?

A review concluded that dieting appears to result in eating binges once food is available (Polivy, 1996), and rats with a history of restriction and refeeding kept bingeing after restriction ended (Hagan & Moss, 1997), but in a randomized experiment a 6-week low-calorie diet decreased bulimic symptoms in nonobese women (Presnell & Stice, 2003).

Does food restriction affect drug use?

In rats, chronic food restriction augments the rewarding effect of diverse drugs of abuse (Carr, 2002).

References