Sweet donuts are unhealthy because the sugar in them causes obesity as does the fat particularly in fried donuts. Savoury donuts are healthy in moderation but they can contain too much fat especially if they are fried. Other products like sweets and toffees are much more harmful. The body of a Christian is the temple of the Holy Spirit. (1 Cor. 6:19-20) We should strive to eat healthily. Any numbers of manufacturers produce tasty and unhealthy foods. They employ high pressure advertising to encourage adults and children to eat unhealthily.
There are problems with Hamburgers and other products as well.