Final answer:
A hypothalamus lesion, diabetes mellitus, Cushing's disease, and low levels of serotonin can contribute to a client's excessive weight gain.
Step-by-step explanation:
Excessive weight gain can be caused by several factors, and in this case, the options that would contribute to a client's weight gain are:
- A hypothalamus lesion, which can disrupt the regulation of hunger and satiety.
- Diabetes mellitus, which can lead to increased appetite and weight gain.
- Cushing's disease, which can cause weight gain due to excessive production of cortisol hormone.
- Low levels of serotonin, which is associated with increased food cravings and overeating.