NFSC 100 Final part 2

Energy Balance, Obesity, and Weight Management

energy balance

the balance between energy intake (diet) and energy output (expenditure)

• when intake = output → weight management

• when intake > output → weight gain

• when intake < output → weight loss

energy intake

calories consumed from foods and beverages, including carbohydrates, protein, fats, alcohol

energy expenditure

the amount of energy (calories) the body uses

what are the 3 main components of energy expenditure?

Basal Metabolic Rate, Thermic Effect of Food, and Physical Activity

Basal Metabolic Rate (BMR)

the minimal amount of energy the body uses to stay alive, including maintaining body temperature, breathing, and pumping blood; varies based on age, sex, and body composition

• makes up 60% to 80% of total energy expenditure

what factors impact a person’s BMR?

more muscle, growth, stress/illness → increase BMR

aging, starvation, low thyroid hormones → decrease BMR

Thermic Effect of Food (TEF)

the energy cost of digesting, absorbing, and processing food

• makes up 8% to 16% of total energy expenditure

Physical Activity

any bodily movement produced by skeletal muscles that results in energy expenditure; varies considerably between individuals and across time

• makes up 15% to 30% of total energy expenditure

Body Mass Index (BMI)

measure used to estimate whether a person is underweight, normal weight, overweight, or obese; risk increases

weight (kg) ÷ height (m²)

What are the BMI categories?

Underweight → < 18.5 BMI

Healthy → 18.5 – 25.9 BMI

Overweight → 25.0 – 29.9 BMI

Obese → ≥ 30.0 BMI

what BMI range is linked to lowest risk of death?

between 20 and 25

• risk increases when BMI rises and declines

what has been the trend in the prevalence of obesity in the US in recent years?

prevalence of obesity has increased over time

• about ¾ of US adults are overweight or obese

• about 1/3 of US children are overweight or obese

what are limitations of using BMI to assess health status?

• doesn’t take into account muscle mass vs. body fat

• doesn’t take into account location of body fat

• varies naturally by age (muscle declines with age)

• doesn’t account for variations in body fat with sex, race, and ethnicity

  • different races and ethnicities have have different cutoffs for health risks

what is an alternative method we can use to assess health risks associated with weight or body composition?

Percent Body Fat → considers variation in cutoffs from different sources

percent body fat

proportion of a person’s total body weight that is made up of fat tissue, used to asses health and disease risk

what are the body fat % ranges (based on percent body fat)?

Men → 18% to 25% is average, above 25% is unhealthy

women → 25% to 31% is average, above 32% is unhealthy

what are the health risks of obesity?

higher risk for chronic diseases (type 2 diabetes, CVD, high blood pressure, stroke, cancers), liver disease, infertility, and reduced overall health

what are the social and psychological consequences of obesity?

stereotyped as lazy and lacking self control

• stigma and bias → judged on appearance, not character

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feelings of rejection, shame, and depression

• ineffective treatments can lead to a sense of failure

what are the health risks of being underweight?

decreased immune function, infertility, higher risk of CVD and stroke

visceral fat

fat stored deep in the abdomen around internal organs (liver, pancreas, intestines); high health risk, especially for CVD

• increases risk of metabolic syndrome → higher inflammation, insulin resistance

subcutaneous fat

fat stored directly under the skin; most visible type of body fat and is less harmful than visceral fat

central (android) obesity

body fat is stored primarily in the upper body and abdomen, leading to an apple-shaped figure; associated with higher risk of obesity-related diseases

gynoid obesity

body fat stored primarily in the lower body, leading to a pear-shaped figure

what are some physiological (inside-the-body) theories about the cause of obesity?

• genetics, epigenetics, and obesity → genes and gene-environment impact our ability to gain or lose weight

• gut microbiome and dysbiosis → imbalance of gut bacteria may affect energy balance and promote weight gain

• thermogenesis and BAT → differences in energy expenditure through heat production (brown adipose tissue) may influence weight gain

epigenetics

how environment and behaviors affect gene function

• can influence tendency to gain weight or stay lean, though our genes haven’t changed

dysbiosis

maintenance of normal gut bacteria

• imbalance may lead to obesity risk

what is the difference in white adipose tissue and brown adipose tissue?

white → energy storage

brown → energy storage and maintenance of body temperature

• heat generating tissue, which may protect against obesity

what are some environmental (outside-the-body) theories about the cause of obesity?

• external cues to overeating → available foods and larger portions override satiation

• food supply

• physical activity → high screen time and sedentary jobs increase risk

• built environment → driving instead of walking, food deserts

food desert

areas where people have limited access to affordable, healthy foods

what are 3 lifestyle components of a successful weight management program?

dietary strategies, physical activity, and behavior modification

• when this isn’t enough, there are medical treatment options, such as drugs and bariatric surgery

what are dietary strategies for managing weight?

• control portion sizes

• eat low energy-density foods (more nutrients/volume, less kcals)

• avoid empty calories

• follow a food guide, ex. MyPlate or keep a food record

• ensure adequate calorie intake (maintain BMR)

• eat high fiber and lean proteins (more satiating)

what are behavior modification strategies for weight management?

• shopping after eating, from a list/app, shop around the perimeter for fresh foods, and read food labels to make educated choices

• planning meals in advance, keep healthy foods at the ready, more activity and less snacking, eat at scheduled times without skipping meals, and drink lots of water

• reduce triggers by storing food out of sight, eating in dining areas, avoiding buffets, and keeping dishes off the table

Glucagon-like peptide receptor agonists (GLP-1s)

weight loss medications designed to mimic the effects of a natural hormone that helps regulate blood sugar and reduce appetite

• recommended in combination with lifestyle strategies

How do GLP-1 drugs differ from older weight loss drugs?

older drugs broadly suppressed appetite and metabolism

new drugs act as a natural hormone

what are the limitations of GLP-1 drugs?

• high cost

• limited supply

• unequal access