Final answer:
Gaining weight is most difficult for those with an ectomorph body type due to their fast metabolism and slender build. The ectoderm gives rise to the skin cells. For weight loss, eating a diet rich in vegetables is most beneficial as they are low in calories and high in fiber.
Step-by-step explanation:
Gaining weight is typically most difficult for individuals with an ectomorph body type. Ectomorphs are characterized by a slender frame and fast metabolism, which can make it challenging for them to put on weight, despite consuming high-calorie diets. In contrast, mesomorphs, with their more muscular build and efficient metabolism, can gain and lose weight relatively easily. Endomorphs, which tend to have a higher body fat percentage, generally find it easier to gain weight than ectomorphs but may struggle more with weight loss.
In relation to the development of skin cells, the answer is ectoderm. The ectoderm is the outermost layer of the embryonic germ layers and is responsible for forming not only the skin but also the nervous system and various other structures.
Concerning weight loss, consuming a diet rich in vegetables can be very beneficial. Vegetables are low in calories, high in fiber, and nutrient-dense, making them a great choice for those looking to lose weight. While lean meats and fruits can also be part of a healthy weight loss diet, vegetables typically have fewer calories per serving and help create a feeling of fullness without adding many calories.