just done an online bmi calculator for DD. At 4 yo, 105cm & 20kg she is 81st centile for height & 94th centile for weight, which makes her obese. Apparently 
Will take her along to the HV clinic rather than rely on that but I am a little surprised. She is stocky rather than slender, you can see her ribs, & she wears 4-5 age clothing. I've seen fat kids & DD doesn't look like them. Are my eyes wrong?