They said amount, not 'calorific value'. Penhaps it was replaced with lower calorie food. But i think there is also the factor that sugary foods/carbs are more

They said amount, not 'calorific value'. Penhaps it was replaced with lower calorie food. But i think there is also the factor that sugary foods/carbs are more addictive and not as satiating as fatty foods (eg 'i'll just have another biscuit', cf. considerable successes of keto diets). Eating something less sugary may have had a knock on effect and reduced the amount of food eaten later.