My Russian SIL who is obsessed with her weight gives my 2 and a half year old niece semi-skimmed milk instead of full-fat. My niece is small for her age and doesn't eat well anyway. SIL says that full-fat makes niece constipated but there's no evidence of this. Any opinions on this please? I feel she's wrong and my brother has no say in her upbringing as he works away a lot.