Thanks all for your replies. It's good to read about other chubby bubbas out there who achieved motor milestones fine. Allays my own fears. Just a shame there's not a specific study to throw back in my Dad's face - although I can't imagine what the measure for 'over-fed' would be.

I do think it has a fair bit to do with genetics. DD is a mini-me. I fed her just as much, but she's always been a long and lanky little thing, just like me and my family. DS is DH all over and he was a huge bubby too (though FF, which led me to wonder the difference) and his family tend to have slower metabolisms and put on weight more easily.

Kuraiza, you didn't offend me! I had wondered whether it might have a little to do with my diet too... not sure whether sugar and fat content of milk changes depending on maternal diet?? I have a super-fast metabolism and am eating huge ammounts of anything and everything (except dairy... siiiiigh) to keep up with what DS is taking out of me. I weigh 2kg less than pre-pregnancy - 60kgs and 6ft tall, I'm guessing the doc would not be thrilled with my BMI. To keep up... and coz I'm a bit greedy... I do eat a very high calorie diet and whilst there's lots of good stuff in there, there's also a fair bit of sugar in my tea, lollies and fish and chips!

If anyone does come across a study pertaining to this, can you post me a link. Not worried now, just quite interested.

Oh, and I agree Arcadia, the only thing that seems to be suffering are my arms and back. Got pretty impressive Mummy-muscles though!!