According to the CDC, severe obesity is defined as having a Body Mass Index (BMI) of 40 or higher. This classification is typically used for individuals whose excess weight puts them at a significant risk for death.

Severe Obesity 

Body mass index (BMI) is a measure utilized by medical doctors to determine if an individual is obese. It uses the formula of weight (kg) divided by height (m^2) squared.

Body Mass Index (BMI)

Being extremely overweight or obese serves as a significant risk factor for a variety of negative health outcomes. These potential consequences include, but are not limited to, an elevated risk for cardiovascular disease, stroke, Type 2 diabetes, liver disease, sleep apnea, infertility, arthritis, and certain types of cancer such as colon and breast cancer.

Health Consequences of Overweight and Obesity

An adult is considered overweight if their Body Mass Index (BMI) is between 25 and 30. For instance, on a standard BMI chart, this category can apply to a person who is 4'11" and weighs between 120-140 pounds, or a person who is 6'6" and weighs between 220-265 pounds.

Overweight (BMI 25-30)

An adult is classified as obese if their Body Mass Index (BMI) is 30 or higher. As an example from a BMI chart, this category could include an individual at 4'11" weighing between 140 and 350 pounds, or an individual at 6'6" weighing between 265 and 350 pounds.

Obese (BMI > 30)

The prevalence of being overweight or obese is a major public health concern in the United States. According to 2018 CDC estimates, approximately 40% of the adult population is obese. Furthermore, nearly three-quarters of all adults and one out of every six children are classified as overweight.

Prevalence of Overweight and Obesity in the United States

The primary recommended approach for managing and improving health related to body weight involves a combination of diet and exercise. However, these methods are not universally successful. For individuals who do not achieve weight loss through these means or whose obesity presents a life-threatening risk, more intensive medical interventions like bariatric surgery may be considered.

Treatment for Obesity

Read the following scenario. Analyze the potential interplay of biological, psychological, and social factors that could be contributing to Alex's weight gain.

Analyzing Contributing Factors to Obesity

Obesity is characterized by an individual weighing more than what's defined as a "healthy" weight for their gender and height. It can be broken into three classifications based on Body Mass Index (BMI):
- Overweight
- Obese
- Severe Obesity 

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Eating is a fundamental motivated behavior driven by the biological need for survival. The regulation of hunger and eating involves complex physiological mechanisms. However, this behavior is not solely biological; it is also significantly shaped by powerful social, cultural, and economic influences. Understanding eating behavior requires examining both the physiological processes and the external factors that affect it, as well as the adverse consequences of disordered eating.

Hunger and Eating as a Motivated Behavior

Spielman, R. M., Jenkins, W. J., & Lovett, M. D. (2020, April 22). Psychology (2nd ed.). OpenStax. https://openstax.org/books/psychology-2e/pages/1-introduction

OpenStax Psychology (2nd ed.) Textbook

Hunger is driven by several physiological signals that prompt feeding behavior. These include physical cues, such as stomach contractions or 'hunger pangs' that occur when the stomach is empty, and chemical messages sent to the brain. A key chemical trigger is a drop in blood glucose levels, which prompts the pancreas and liver to release signals that initiate the drive to eat.

Physiological Mechanisms of Hunger

Obesity 

In contrast to the widespread issue of being overweight, a significant minority of the population suffers from eating disorders, which commonly lead to being underweight. These conditions, such as bulimia nervosa and anorexia nervosa, are often characterized by an intense fear of gaining weight and can result in numerous negative health effects.

Eating Disorders 

Beyond the biological drive for sustenance, eating behavior is heavily influenced by a variety of non-physiological factors. These include social contexts, cultural norms and traditions related to food, and economic conditions that affect food availability and choice.

Non-Physiological Influences on Eating Behavior

Satiation, the feeling of fullness that stops eating, is controlled by several physiological signals sent to the brain. Key mechanisms include rising blood glucose levels, which cause the pancreas and liver to send 'shut-off' signals; feedback from the passage of food through the gastrointestinal tract; and the release of the satiety hormone leptin from fat cells.

Physiological Mechanisms of Satiation

The brain acts as the central command center for regulating eating by integrating the various physiological signals for both hunger and satiety. This integration process, which occurs in key areas like the hypothalamus and hindbrain, ultimately determines whether an individual engages in feeding behavior.

Brain's Integration of Hunger and Satiety Signals

The regulation of eating can be understood as a cycle that begins with hunger, a signal initiated in the brain's hypothalamus. This drive leads to the consumption of food. After eating, satiety signals, originating from the stomach, contribute to a feeling of fullness and satisfaction, which in turn stops the eating behavior.

The Hunger-Satiety Cycle

An individual's body weight is influenced by a complex interplay of factors. These include biological elements like gene-environment interactions and metabolic rate, behavioral aspects such as the balance between calories consumed and expended, and broader societal factors like socioeconomic status and the physical environment.

Factors Determining Body Weight

Analyze the individual's behavior in the following scenario. Explain which factors are likely influencing their decision to eat, distinguishing between their physiological state and other potential influences.

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