Why soup? It's because there has been substantial research investigating why soups make you feel full relative to the number of calories you consume. There are some these papers listed below if you want to have a look, but the main point is:
Soup makes you feel fuller sooner and for longer (research proves this).
Therefore you consume less calories and lose weight. This is something that can be sustained as it is proper food containing all the necessary components of the food itself (fibre etc), which is why juicing can never be sustained more than a few days (and then the weight goes back on).
A BPM fave is to cram in 230-235g of whatever the main ingredient would be into a 400ml tub; at the moment, we've Butternut Squash (108 cals), Tomato & Basil (108 cals) and Carrot & Coriander (152 cals).
These are enough for most people to have as an actual meal but should you need something else, then a piece of fruit works really well. Ps, don't let people tell you fructose is bad...fructose seems to be banded along with high-fructose corn-syrup (they're most definitely not the same thing!) Also, fructose is actually low-medium glycemic load and not at all like other sugars like glucose and sucrose.
Hunger is impossible to beat. You simply can't win. If you're a chunky body-type, your relationship with satiety hormones (ghrelin and leptin) is different from a slimmer body-type so ideally you'd employ a smarter method to combat hunger. Soup is the most practical way of doing this.
The health and fitness info that BPM Bike Lab advise is always backed up by peer-reviewed scientific research, which is actually unusual in this unregulated field. For more info on the science about why soups makes you feel full etc, have a look at the papers listed below.