If you could, try cutting down on the eating, have a little over a serving then once you're used to that, go to a regular serving.
You may have heard of the Slim Fast diet. Slim Fast is high in sugar and isn't that healthy. I've tryed using it but it only made me hungry all the time, and made me want more than I did before I started Slim Fast. I'm not sure if it'll do that for you but maybe you should atleast give it a try.
Then I started drinking Red Bull. It's an energy drink, and fills you up easily. I lost 20 pounds in 2 weeks when I had Red Bull. I'm a very lazy person, and I stay up all night, and sleep more than half the day. I never excercise, I sit on the couch almost the whole time I'm up. But I drink Red Bull. And it has helped so much.
Another good thing about Red Bull is that it's healthier than Slim Fast.
A bad thing is that it cost about $2 a can. It's totally worth it though.
You'll be able to keep up with your 4 year old.
If you're not able to do the Slim Fast diet, or drink a Red Bull instead of eating a meal, then you do need to talk to your doctor to see if there's some pill that could help you lose the weight.
Do NOT consider surgery!!!! It's very dangerous, and may leave scars.
I hope this has helped. If not, there are ways to lose weight.