In which condition is truncal fat predominantly seen?

Truncal fat is predominantly associated with Cushing's syndrome, which is characterized by an excess of cortisol in the body. This hormonal imbalance leads to a redistribution of body fat, resulting in an accumulation of fat around the trunk and abdominal area. Patients with Cushing's syndrome often exhibit a characteristic "moon face" and buffalo hump, which are indicative of this specific pattern of fat distribution.

In contrast, while type 1 diabetes can lead to a range of metabolic changes, it is not typically associated with truncal obesity. Hypothyroidism can lead to weight gain, but this is usually more evenly distributed and does not specifically manifest as truncal fat. Osteoporosis is a condition related to bone density and does not influence fat distribution in the body. Therefore, the link between Cushing's syndrome and truncal fat is well-established, making it the correct answer in this context.