There are many foods that looked at out of context aren't particularly "healthy" if considered against an average modern sedentary lifestyle but which are sources of either quick energy or useful protein which can be beneficial for weight management and overall health if properly utilized.
All of this is why talking about diet without also talking about exercise is useless.
My completely non-scientific belief is that while over-consumption of sugar isn't a great thing, the primary thing making us fat is that we've switched to a massively sedentary lifestyle on average. We aren't toiling in the factory or on the farm or walking door to door selling vacuums, and mostly that's a good thing because those jobs aren't particularly interesting for many of us, but at the same time our bodies aren't really evolved for sitting down 8-16 hours a day.
Once every 2 months or so, I buy one of these[1]. But there's no way it can be "part of a healthy diet just like anything else", as the person I replied to seems to think. It is an exception to my healthy diet, not part of it. I deviate from my healthy diet once every 6 - 8 weeks to indulge. I'm also aware of Micheal Phelp's diet[2] would work for me too if I could swim back & forth for at least 4 hours a day instead of standing[3] in front of a computer for 8+ hrs.
1. http://www.militarydiscountscentral.com/wp-content/uploads/2...
2. http://blogs.wsj.com/health/2008/08/13/the-michael-phelps-di...
3. I have a standing desk and never use my chair.
When you say "doughnut" you mean this[1], right? If so that's 100%, Grade A nonsense and abruptly ends any consideration I was giving your comment.
1. http://twincitiesdonut.com/images/donut.jpg