Genetic Influences on Body Size
Have you ever heard anyone say that you look like your parents or other family members? Through research studies done on specific genes and their effects, it has been found that BMI similarities and risk for obesity exists between first-degree relatives. Obese children often have obese parents. Even with taking into consideration environmental factors, it has been found that adopted children’s adult weight mostly is similar to their biological parents.
Where these genetic factors’ influence comes in is through the amount of production or mutations in the receptors of the hormones leptin and ghrelin. They have a role in the complex system of regulation of body fat and weight. Leptin influences the amount of food intake and long-term appetite. The size of body fat stores are influenced by messages from leptin to the brain. Ghrelin, which is produced in the stomach, is part of the human survival mechanism that reacts to weight loss and increases appetite in humans. It makes it hard to maintain weight loss that is from restricting your food intake.
There is not just one part of the human genetic structure that affects fatness or thinness. Tendency towards being overweight has many causes both genetic and environmental. Influences come more often from susceptibility genes or those that do not produce a certain characteristic, but make the person more likely to gain weight in response to their current setting. Genetics affects our level of metabolic efficiency or how much or how little food intake you require to maintain your resting metabolic rate, amount of energy needed to digest your food (TEF), and calories burned during light exercise. Genes also influence our ability to use the fat we eat for energy, taste preferences for high fat vs. lower fat foods, and ability to achieve a high level of physical fitness.