Final answer:
The majority of an extra twenty pounds gained by an adult will likely be fat, as unused energy is stored in the body as adipose tissue. Obesity, defined as a BMI of 30.0 kg/m² or higher, is often caused by chronic overeating and is linked to several health complications, including type 2 diabetes and hypertension.
Step-by-step explanation:
When an adult gains an extra twenty pounds of body weight, a significant portion of this weight is likely fat. This is because any unused energy in food, whether it comes from carbohydrates, proteins, or lipids, is stored in the body as fat. If you take in more energy than you use, this surplus energy will be stored, leading to weight gain that is predominantly adipose tissue or fat. It's important to note that obesity is described as having a body mass index (BMI) of 30.0 kg/m² or greater, and this condition is often caused by chronic overeating and is linked to various health issues such as type 2 diabetes and hypertension. Obesity should be considered a preventable condition, and addressing dietary habits is essential for maintaining a healthy body weight and preventing the associated health risks.
It is worth noting that not all of the twenty pounds would necessarily be fat, as weight gain can also include increases in muscle mass, water retention, and other factors. However, in the absence of a significant increase in muscle mass due to resistance training, or other specific conditions affecting body composition, a majority of the weight gain would likely be fat.