Zak Hessey was 8kg (17lb 6oz) when mum Lisa took him to hospital, telling doctors he was a "fussy eater" and not gaining weight.
Medics said he should weigh 9kg (19lb 8oz) and advised the mum of five to bulk him up on crisps, chocolate and cakes. When she said no, social workers were called in and her tot was put into foster care to assess if his eating improved.
Healthy eater Lisa, 28, and her HGV driver husband Paul, 48, battled through the courts for four months before they got their son back. Social workers then admitted in court that the couple, from Bolsover, Derbys, were devoted and loving parents.
Angry Lisa claims Zak's time in care left him a "chocoholic" and just 250g (8oz) heavier.
She said: "I thought I was doing the right thing going for help when Zak began refusing to eat and lost weight. "Instead they basically accused me of neglect. They said I should give him chocolate, cakes and junk food just to get calories into him."
Lisa said she was warned her parental rights could be removed if she took legal action.
She added: "The Government and doctors always drum into parents the importance of healthy eating - yet they were telling us to feed Zak all the wrong things.
"Now it's hard to get him to eat anything else."
Back home, Zak has gained weight and is "doing well", she said. A Chesterfield Royal Hospital spokesman said: "We believe we acted in Zak's interest."