Separately, these two things don't contribute to any statistically significant amount of weight loss, but when you put them together, they appear to act synergistically.

这两种物质单独使用时，没有明显的减肥作用，但若将二者结合，它们则具有协同作用。

Separately, these two things don’t contribute to any statistically significant amount of weight loss, but when you put them together, they appear to act synergistically.

单独来看，这两件事对减轻体重没有任何统计意义，但当你把它们放在一起时，它们似乎协同作用。