PowerPoint® Presentation by Jim Foley Motivation and Emotion © 2013 Worth Publishers

Module 29: Hunger

Topics you might be hungry to learn about Hunger:  Body Chemistry and Brain control of Hunger  Cultural and Situational effects on Hunger  Obesity and weight control challenges: Physiology, social factors, food and activity factors

A closer look at one need/motive: Hunger Research on hunger is consistent with Abraham Maslow’s hierarchy:  In one study, men whose food intake had been cut in half became obsessed with food.  Hunger even changes our motivations as we plan for the future.

Physiology of Hunger  Experiments and other investigations show a complex relationship among the stomach, hormones, and different parts of the brain.  Feeling hungry can include stomach contractions; the feeling can happen even if the stomach is removed or filled with a balloon.

Receptors in the digestive system monitor levels of glucose and send signals to the hypothalamus in the brain. The Hypothalamus and Hunger The hypothalamus then can send out appetite- stimulating hormones to tell the body: time to eat!

The Body Talks Back to the Brain The hypothalamus sends appetite-stimulating hormones, and later, after eating, sends appetite- suppressing hormones. Hormones travel from various organs of the body back to the brain to convey messages that increase or decrease appetite.

Regulating Weight  When a person’s weight drops or increases, the body responds by adjusting hunger and energy use to bring weight back to its initial stable amount.  Most mammals, without consciously regulating, have a stable weight to which they keep returning. This is also known as their set point.  A person’s set point might rise with age, or change with economic or cultural conditions. Therefore, this “set point” of stable weight is more of a current but temporary “settling point.”

Which foods to eat? Taste Preferences  Some taste preferences are universal. Carbohydrates temporarily raise levels of serotonin, reducing stress and depression.  Other tastes are acquired and become favorites through exposure, culture, and conditioning.  Different cultures encourage different tastes. Some cultures find these foods to be delicious: reindeer fat and berries, or roasted guinea pig.

Biology, Evolution, and Taste Preferences Differences in taste preferences are not arbitrary. Personal and cultural experience, influenced by biology, play a role.  We can acquire a food aversion after just one incident of getting sick after tasting a food.  It is adaptive in warm climates to develop a taste for salt and spice, which preserve food.  Disliking new tastes (neophobia) may have helped to protect our ancestors.

How much do we eat? Eating depends in part on situational influences.  Social facilitation: the presence of others accentuates our typical eating habits  Unit bias: we may eat only one serving/unit (scoop, plateful, bun-full) of food, but will eat more if the serving size is larger  Buffet effect: we eat more if more options are available

Influences on Eating Behavior

Do we need to control our hunger?  When we eat enough to noticeably gain weight, we can face discrimination, bullying, and depression.  Standards for body size can vary in different cultures, sometimes creating an unhealthy norm of being overweight or underweight.  Body fat has been seen as a sign of affluence, and thus has been considered attractive.  But at a certain ratio of weight to height, health risks arise.

The Physiology of Obesity  Having some body fat is normal and healthy; fat stores energy.  Being mildly overweight is not necessarily a problem if the person is in good physical condition or exercising.  Obesity can lead to health problems, including diabetes, heart disease, cognitive decline, and some cancers.  The physiology of obesity can also make it hard to lose weight, due to set point/metabolism, genetics, appetite, and lifestyle factors.  Obesity, and losing weight, is not just an issue of motivation.

Set Point and Metabolism  For a variety of reasons, a person’s set point, the stable weight the body keeps returning to, drifts from a healthy weight.  Those who becomes overweight develop a new set point that is now hard to shift. Why?  Once the set point has shifted, metabolism shifts to maintain it; resting metabolism slows.  Starving to lose weight slows metabolism further.  Hunger kicks in when weight goes below he new set point.  Because the body works this way: It is thus easier to stay lean than become lean.

The Genetics of Obesity  Adopted siblings eating the same meals end up with a BMI/weight resembling biological parents, not people in the same household.  Identical twins have similar weights, even when raised apart with different food.  There seem to be many genes with effects on weight. Lifestyle Factors and Obesity  People who are restless and fidgeting burn off more calories and gain less weight than others.  Inadequate sleep causes weight gain, despite increased active time, because of appetite hormones.  Having an obese friend correlates with becoming obese.  Sedentary lifestyles and fast food may be leading to increased body fat worldwide.

Rates of being overweight Projected  BMI (body mass index) >30: Obese Prevalence of Obesity 1 billion people worldwide are overweight, 300 million of which are obese (BMI >30).

How does obesity develop, and why is it hard to change?  It was adaptive for our ancestors to crave energy-rich food when available.  Problem: energy-rich ‘junk’ food is now easily available, and cheaper than healthy food  It is adaptive to slow down our burning of fat when food is scarce.  Problem: in poverty or in crash diets, our body can slow down weight loss Obesity and Weight Control

Losing Weight: The Challenge If you decide to move your body’s set point to a lower body weight: Because of the physiological factors and perhaps due to lifestyle and peer issues:  once obese, weight loss is difficult, and permanent weight loss is even harder.  obsessive weight loss attempts can add to shame, anxiety, depression, and disordered eating habits.  Begin with an understanding of the metabolic challenges you face, so that you blame slow progress on physiology, not poor willpower.  Begin with self-acceptance and a decision to change, rather than feeling shame.  Make gradual and consistent, not drastic and varying, lifestyle changes.  Increase exercise and healthy food choices.  Get support. Losing Weight: The Plan