• I’m not a fitness fanatic, but I try to work out three times a week.

讲解
a … fanatic：非常热衷…的人
fitness：健康
work out：健身

My weight has gone up and down for years. I just can’t seem to stick to a diet.

讲解
weight：重量、体重
go up：上升
go down：下降
for years：很多年了
can’t seem to … ：看起来总是不能…
stick to a diet：坚持节食