This forum is about wrong numbers in science, politics and the media. It respects good science and good English.
The mind boggles -- Milk, meat pies, etc are all Junk food and killing (making obese) our kids. Apparently the child in the picture is obese. He appears normal to me.
What is the ideal diet?
You cannot win this debate. Getting someone to recognize that the beginning of the discussion is "What keeps me alive", NOT "What is optimum" is really difficult. People fooling around with optimum are fiddling with the buffer zone between "enough to make sure I don't die tomorrow" and "so much that I do die tomorrow". (That zone is REALLY big). You could refine it better than that, but this is now in the realm of entertainment. Sitting around shooting the breeze over a subject like this is good fun (well for some of us). It is not absolutely necessary.
This excludes people with real medical conditions that do need to pay close attention to what they eat because it might kill them. Peanut allergies and the like.
Why is "fast food" synonymous with "junk food"?
Most of the most unhealthy stuff I have ever eaten has been in expensive restaurants and was lovingly hand-prepared by a team of dedicated professionals. By comparison almost anything a harrased mum can shove in the microwave is virtuous, even if it could be made with better cuts, fresher vegetables and so on.
OK, James, what is "unhealthy" food. Nearly all the food I eat is so unhealthy it's actually dead! I read a lot of tosh about trans- fats, etc., etc. but the 'milieu interior' is virtually unchanged by what goes in through the mouth, as all the nonsense about salt illustrates. All digestive systems have had about 4.5 milliard years of development to ensure they can live in wildly varying chemical environments while keeping their internal works constant. (Have a shufti at James LeFanu's book "The rise and fall of modern medicine" for details).
That being said, there are substances that do get into the body and do harm (as you well know, being a biochemist) - we call them toxins.
And if I drink too much water it becomes...
Somehow we need to create a virtual Pub.
This forum seems to be one of the last bastions of sanity in the world.
By "unhealthy" I mean foods with an excessive concentration of fats (of any sort) and refined sugars. It's actually easier to find this kind of stuff in top-tier restaurants than typical "junk food" restaurants. I would eat a burger every day if I felt like it, but perhaps leave the chips most of the time.
You really have to prepare your own food to see what calorie bombs some of this stuff can be. I'm really not into desserts, but dinner guests generally are. So I invested in an ice cream maker because you can produce almost zero-effort desserts. An example recipe:
200g cheap (high-sugar) white chocolate
250ml double cream
1 beaten egg white
So the best part of half a day's calorie requirement for an active man in one dessert.
I agree there's not really such a thing as "unhealthy food" but there are unhealthy diets, consisting of excessive quantities of the food labelled "unhealthy".
There's another thing to bear in mind, which is that the body's own weight control system is pretty accurate even in the most obese. If you are 10kg overweight then in your entire lifetime you have eaten the equivalent of 10kg fat beyond requirements (neglecting the fact that if you are fatter your basal metabolic rate is a bit higher). Divide that by the amount of food you have eaten, and to have not put on that weight, work out what fraction of a grain of rice per meal you should have left at the side of the plate. It is a myth that fatsos are constantly gorging themselves on buckets of ice cream and burgers. You don't need to overeat by much to put weight on.
Precisely my point. I'd dispute that "unhealthy" foods are necessarily those that have an excessive concentration of fats or sugars, though. As James so rightly said, it is the diet that can be unhealthy (but very rarely is). H. sap. is a generalist par excellence and usually eats a varied diet, so it is entirely reasonable for one particular food in that diet to be virtually pure fat (lard) or sugar (honey). Both have been eaten from time immoral and we're still here.
Although I hear much about the dangers of being overweight, etc. my very small sample of local acquaintances shows exclusively that those who have suffered heart attacks and strokes have tended to be on the skinny side, and the fatties are still generally wobbling along fine.
By no means is that a representative sample, I know, but it does make one wonder, particularly in the light of our guru's "The Epidemiologists" and James Le Fanu's "The rise and fall of modern medicine" which do a pretty fair hatchet job on Ancel Keys demonisation of fats.
While I know that trans- fats are generally produced in margarine production by splitting double C-C bonds, do they not also occur in nature? I don't recall any particular reference to them in biochemistry, though that was forty years ago and things have moved on a bit since.