I was talking recently with a friend who's given up eating meat and she found that she was much hungrier and needed more snacks.
This actually isn't surprising if you think of the macronutrient content of meat. Both the fat and protein content slow stomach emptying and digestion delaying hunger.
Anyone who's ever followed a very low-fat eighties style diet will know that without enough fat you can develop an insatiable appetite which no amount of carbs can satisfy. If you are following a low-fat vegetarian or vegan diet where you mainly eat pulses, wholegrains and vegetables you're likely to be digesting your food quicker meaning your stomach will be empty sooner and your hunger will kick in sooner.
I have also dramatically cut down on my intake of meat in the last six months and have to say my portion sizes have gone up as a result. Not to say I've put on weight, I've actually lost some during meat free BeachCamp, but I've definitely felt less satisfied from my main meals than when I have oily fish or meat.
Adding eggs, fish, tofu and low-fat diary products is an easy way to remedy this, bringing more protein to the meal. However it's also worth remembering that both fats and fibre are also necessary to satisfy your appetite.
Unless a meal contains oily fish make sure you add a source of essential fats - flax or olive oil, olives, avocados, nuts and seeds all work.
Also make sure any low-fat or low-protein meals contain plenty of roughage - so raw fruit or vegetables or pulses.
Following these tips should leave you feeling satisfied without having to eat meat.