Biological influences on body weight include genetics (such as the FTO-associated gene), metabolic factors (such as low levels of thyroid hormone), and physiologic factors (such as abnormal levels of various appetite-regulating hormones). From the list below, choose all the correct statements about biological influences on body weight. a. Obesity is associated with lower amounts of UCP1.
b. The thrifty gene theory suggests that people with this gene universally expend more energy compared to those without the gene.
c. The set-point theory suggests that the body responds to both energy restriction and overeating with physiological changes to maintain its weight within a narrow range.
d. Genetic factors account for 20 to 50% of a person’s BMI.
e. People who have the fat mass and obesity (FTO)-associated gene are generally heavier than those without the gene.

a. Obesity is associated with lower amounts of UCP1.

c. The set-point theory suggests that the body responds to both energy restriction and overeating with physiological changes to maintain its weight within a narrow range.

Explanation:

Correct statements:

a. Obesity has been associated with a low expression of the UCP-1 gene in the brown adipose tissue. For example, in transgenic mice, it has been shown that the overexpression of the UCP1 gene is associated with the stimulation of fatty acid oxidation.

c. The set point theory indicates that the human body has a preconfigured weight which is based on information contained in the genome. In consequence, the set point theory states that fluctuations in weight are limited, where there are people that have higher weight set points compared to other persons, and inherent natural mechanisms in the body try to maintain within these ranges.

Incorrect statements:

- Genetic factors account for 50-80% of the body mass index (BMI). The remaining value is due to environmental factors and the interaction between a genotype and the environment.

- The Fat mass and obesity-associated gene (FTO) is a gene located on chromosome 16 which encodes for the alpha-ketoglutarate-dependent dioxygenase enzyme. Although it has been suggested that some allelic variants of this gene are associated with obesity, this gene is always expressed (i.e., constitutively expressed) in the hypothalamus, where its expression is linked to the food intake.

- The 'thrifty gene' theory states that gene variants (alleles) evolved to favor a more efficient use of nutrients, thereby promoting diseases associated with an excess of calories such as obesity and type 2 diabetes.