Hello, I am struggling to understand 5.1.

Nutritionists have noticed that since the fast food boom of the 1980s, there has been a surge in obesity rates. Consequently, almost all of this surge can be attributed to decreased physical activity and changes in dietary habits.

The latter sentence explains the first sentence and acts as the why. Wouldnt that be the premise? Whilst the observation of nutritionists stands as the conclusion?

Hi, I got a bit confused. So strong arguments = no assumptions. However, the strength of an argument depends on the reasonableness of the assumption. Can someone please explain this to me.