It's obvious that not all foods contain the same amount of calories. It depends on their composition (water, fibre, fat, protein and carbohydrate content). 100g of courgettes isn't going to have the same impact on the waistline as 100g of yogourt. In other words, while you can stuff yourself with all the green beans you like, unfprtunately you can't stuff yourself with chocolate bars, because they have a high calorie density.
Here are some examples of calorie density equivalents:
15 fresh grapes (100g) = 70 kcal = 15 raisins (10g)
1 bar of chocolate (60g) = 270 kcal = 13 slices of fresh pineapple (500g)
1 crème brûlée (100g) = 300 kcal = 6 fat-free fruit yogourts (750g)
1 portion of chips (160g) = 450 kcal = 22 portions of courgettes (3.5 kg)