When baby rats are given too much food right after birth, they actually have higher 'good cholesterol' when they're young, but as adults (around 6 months), they end up with lower 'good cholesterol' levels compared to normally fed rats.

The study fed baby rats extra milk by putting them in small litters (only 3 babies per mom instead of 10). At 21 days old (weaning), these overfed babies had higher HDL (good cholesterol). But when they grew up to 180 days old, they had lower HDL cholesterol - exactly what the claim says would happen.