From a nutrition article by Shane Bilsborough in today's Herald Sun:
In a recent exercise, people were fed meat and pasta, but beforehand were fed vegetables at three different amounts: 180g, 270g and 360g. When researchers gave people 360g of vegetables (and, let's face it, every one of us needs to eat more vegetables), people ate 14 per cent fewer calories.
A 300g salad eaten before lunch resulted in 12 per cent fewer calories consumed at lunch, while an entree soup (even canned) cut lunch portions by 30-50 per cent.
...It seems the human body detects a certain amount of food (or volume). Once this amount has been reached, a signal is sent to the brain to stop eating or to say, "I'm full".
Vegetables (and vegetable soup) and salads eaten before a main meal contain fibre, which is filling, vitamins, minerals and antioxidants, and are about 80 per cent water. Hence they add considerable weight, and promote the feeling of fullness without the calories.
'What Are Your 4 Pounds Made Of?' is an article along similar lines noting that most humans eat around 3-5 pounds of food per day. 'Indeed, as we approach 4 pounds of food intake for the day, most of us are feeling pretty satisfied. Now, this can be 4 pounds of celery. Or it can be 4 pounds of candy bars. It’s not the food or calorie content that matters. It’s the volume/poundage that counts.' Click here to read more.