Evolutionary Psych-Class 14

anorexia, bulimia, binge eating

•Anorexia nervosa (AN) involves severe restriction, while bulimia nervosa (BN) includes bingeing and purging.

•Binge eating disorder (BED) lacks purging but involves loss of control over eating.

gender differences for eating disorders

•Men with eating disorders often focus on muscularity rather than thinness.

•Gender differences may be influenced by evolutionary pressures on body image.

cultural factors for ED

• mor common in west

• media promotes unrealistic body ideals

• non-western with rapid modernization show rising rates of ED

• social media exacerbates: intrasexual competition, especially among young women

global trends in overweight and obesity

•Since the 1970s, global obesity rates have nearly tripled.

•In 1975, approximately 4% of adults were obese; by 2016, this figure rose to over 13%.

•As of 2021, more than 2.1 billion adults worldwide are overweight or obese.

•By 2050, it's anticipated that over half of adults globally will be overweight or obese.

obesity variations across gender

•Globally, obesity prevalence is higher among women (15%) compared to men (11%).

•In Africa, nearly half of women are projected to be overweight or obese by 2030.

•Men are more likely to store fat in the abdomen, increasing risk for cardiovascular disease.

•Women tend to store fat in the hips and thighs, influenced by reproductive hormones.

racial and ethnic disparities in obesity

•In the U.S., 57% of African American women were considered obese in 2014.

•Obesity rates among Hispanic populations are significantly higher than among white populations.

•Cultural dietary habits and socioeconomic factors contribute to these disparities.

•Indigenous populations worldwide have some of the highest obesity rates due to nutrition transitions

geographical differences in obesity rates

•United States: Obesity rates have risen from 13% in 1962 to 42.4% in 2017–2018.

•Japan: Maintains one of the lowest obesity rates among OECD countries at 3.2%.

•Mexico: Among the highest global obesity rates due to increased processed food consumption.

•Africa: Urbanization and lifestyle changes have led to increasing obesity rates, particularly among women.

cultural and societal influences on obesity

•Westernization has contributed to rising obesity rates in developing countries.

•Traditional diets, such as in Japan, contribute to lower obesity rates.

•Socioeconomic status influences food choices and access to healthy options.

•Sedentary lifestyles and urbanization play a key role in increasing obesity rates.

evolutionary foundations of eating disorders

•Eating disorders may result from evolutionary mismatches between past and present environments.

•The human brain evolved under conditions of food scarcity, not abundance.

•Modern food availability and media-driven ideals create maladaptive eating behaviours.

•Intrasexual competition may drive disordered eating in some individuals.

the role of evolutionary mismatch

•• The human lineage adapted to periods of famine and feast.

•• Constant food abundance disrupts ancestral satiety and hunger mechanisms.

•• High-calorie, processed foods override normal regulatory processes.

•• The modern environment pressures individuals into restrictive eating patterns.

Female Competition and Eating Disorders

•Evolutionarily, females competed for mates partly through physical appearance.

•Thinness may signal youth, fertility, and health in mate selection.

•The rise of social media intensifies intrasexual competition.

•Some eating disorders may stem from extreme manifestations of these pressures.

The reproductive suppression hypothesis

•Some women may unconsciously suppress reproduction in stressful conditions.

•Anorexia nervosa could be an adaptive mechanism to delay fertility.

•Evolutionarily, low body fat was a signal of inadequate resources for pregnancy.

•This theory aligns with the high prevalence of amenorrhea in AN.

The adapted to flee famine hypothesis

•Some researchers suggest AN symptoms mimic a survival mechanism.

•Individuals with AN exhibit hyperactivity and lack hunger signals.

•This behaviour could have facilitated migration during times of famine.

•However, this theory struggles to explain modern persistence of AN.

The parental manipulation hypothesis

•This theory suggests some parents may unconsciously suppress daughters' reproduction.

•In some species, younger members assist kin rather than reproduce.

•In traditional societies, unmarried daughters often support family units.

•Limited empirical support exists for this theory in eating disorders.

The Insurance Hypothesis

•The body stores fat as a buffer against future food shortages.

•Modern environments eliminate food scarcity but retain fat-storing mechanisms.

•This hypothesis helps explain obesity but is less relevant to restrictive eating disorders.

•Food insecurity in early life is linked to later disordered eating

The Social Threat Hypothesis

•Eating disorders may function as responses to social threats.

•Food restriction could be a way to avoid social interactions or conflicts.

•Anorexia could serve as a submissive strategy to reduce perceived competition.

•Some research suggests eating disorders correlate with social anxiety.

The sexual competition hypothesis

•Women in highly competitive environments may develop disordered eating.

•Thinness may signal high status and attractiveness.

•Increased exposure to idealized images intensifies this competition.

•This hypothesis has strong empirical support

Male Eating Disorders in Evolutionary Context

•Men more often exhibit a drive for muscularity than thinness.

•This aligns with evolutionary pressures for physical strength and dominance.

•Some men develop muscle dysmorphia, mirroring female anorexia.

•Male body image concerns are increasing in modern societies.

The drifty gene hypothesis

•Obesity may be a result of relaxed selection against excessive fat storage.

•Historically, food shortages maintained body weight balance.

•Modern lifestyles remove the selective pressure against weight gain.

•This theory contrasts with the 'thrifty gene' hypothesis.

evolutionary explanations for binge eating

•Binge eating may have been an adaptive response to food scarcity.

•The drive to overconsume was beneficial in unpredictable environments.

•Modern environments provide constant access to high-calorie foods.

•This contributes to the loss of natural appetite regulation.

evolutionary role for satiety signals

•Humans evolved to respond to fluctuating food availability.

•Satiety hormones (e.g., leptin, ghrelin) evolved to regulate intake.

•Modern processed foods bypass natural satiety cues.

•This leads to overconsumption and disordered eating patterns.

epigenetic factors in eating disorders

•Early life stressors can lead to epigenetic modifications affecting stress response systems.

•These changes may influence vulnerability to eating disorders.

•Research indicates that environmental factors can alter gene expression linked to appetite regulation.

•Understanding epigenetics offers new avenues for treatment and prevention.

Hormonal influences and life stages

•Hormonal fluctuations during puberty, pregnancy, and menopause can impact eating behaviours.

•Midlife hormonal changes may trigger or exacerbate eating disorders in susceptible individuals.

•Awareness of these factors is crucial for timely intervention and support.