Yes, as long as they're healthy. If your kid has a medical condition, I recommend consulting with a knowledgeable pediatrician who truly understands the human metabolism and isn't blindly following the USDA guidelines. Kids and diet are sensitive topics and you can end up in pretty heated discussions with friends, family and even pediatricians and nutritionists who know little about the impact of diet on our health. Our pediatrician appreciates the expertise about food and diet we have accumulated over the years and encourages us to apply it to both of our kids. If your pediatrician is against paleo or keto, discuss the scientific evidence with him or her and point out the dramatic increase in childhood obesity over the past two decades as a sign that the government guidelines have not worked. If all that is fruitless, consider finding another pediatrician who has more expertise in those areas and who is willing to work with you. Our older daughter has been on paleo since she was two years old and our youngest son has been following our diet since he was born (prematurely). Even before I started keto, our kids have been deriving most of their calories (~60-70%) from fat and protein. The other day, my daughter agreed to a spontaneous blood test — when she saw me doing it — and she was in deep nutritional ketosis (1.8 mmol/L).