I was trying to answer the question "why do people think processed foods are bad, and in what way?". My answer was "because processed foods are the only remaining strictly diet-based possibility for a cause of obesity". That is, if we were to ascribe obesity exclusively to a particular diet choice, the only plausible diet choice is "processed foods" - all the others we've tried have clear counter-examples.
Note that I'm not saying we should do this - I believe obesity is much more likely caused by a wide array of lifestyle factors that no study to date accurately controls for (including diet, exercise, stress, environmental factors, mental status, medication etc), not a single dietary style.
Now, "processed foods" is indeed a very vague term, and people tend to include/exclude different foods based on their pet theory of what may lead to the link "observed" in the previous paragraph.
For example, some people strongly believe that glycemic spikes are strongly coupled with diabetes and obesity, and they would include things like fruit juices (as opposed to eating whole fruits) into this category, as well as high glycemic index foods such as bread (in both cases, even home-made ones).
Other people believe that certain additives are likely to have undocumented side-effects, so they will tend to only include foods with synthetic additives, such as preservatives and food colouring, but exclude traditional highly processed foods such as bread or butter as long as they are home-made without additives.
Yet other groups believe the correlation is related to palatability and/or satiety, so they will consider processed foods to be any foods which contain high ratios of palatable substances (like fat, sugar, salt, MSG, other flavour enhancers) to less palatable macro-nutrients. These people would probably include home-made fruit juice or ramen into the processed foods category, but may exclude things like pickles.
This sort of gets to the heart of the problem I have with "processed foods are bad". It doesn't feel meaningful because of how vague it is. If I point at butter and ask "is this processed food" the answer is yes or no depending on the person I'm talking to. That makes it hard to trust the claim "processed food causes obesity". Well, maybe it does? Maybe it doesn't? Pickles don't likely cause obesity (they are very low calorie), so it feels unfair to lump them in the same category as cake, for example.
If it's unreasonable to pin down what is processed, it seems unreasonable to make a claim about the effects of processing.
In a way everything we eat is processed and processing is not necessarily harmful. To take your example of butter, organic butter may be completely different than mass produced butter regarding it's health implications. And this applies to nearly all food. Mass produced tomatoes will be poor in micro-nutrients and contaminated by pesticides. Et cetera.
Our understanding of nutrition and health isn't keeping up in pace with innovations in the food industry. And due to the scale and depth of it I think it's unavoidable that many small bad things will sum up over time leading to health problems without a clear root cause.
Reasons why "processed" food might be bad for health:
- skewed omega-3/omega-6 ratio
- micro-nutrients depletion
Also it's just not economical or environmentally sustainable to feed everyone with "real food". At least not without radical change and trade-offs in other areas.
Note that I'm not saying we should do this - I believe obesity is much more likely caused by a wide array of lifestyle factors that no study to date accurately controls for (including diet, exercise, stress, environmental factors, mental status, medication etc), not a single dietary style.
Now, "processed foods" is indeed a very vague term, and people tend to include/exclude different foods based on their pet theory of what may lead to the link "observed" in the previous paragraph.
For example, some people strongly believe that glycemic spikes are strongly coupled with diabetes and obesity, and they would include things like fruit juices (as opposed to eating whole fruits) into this category, as well as high glycemic index foods such as bread (in both cases, even home-made ones).
Other people believe that certain additives are likely to have undocumented side-effects, so they will tend to only include foods with synthetic additives, such as preservatives and food colouring, but exclude traditional highly processed foods such as bread or butter as long as they are home-made without additives.
Yet other groups believe the correlation is related to palatability and/or satiety, so they will consider processed foods to be any foods which contain high ratios of palatable substances (like fat, sugar, salt, MSG, other flavour enhancers) to less palatable macro-nutrients. These people would probably include home-made fruit juice or ramen into the processed foods category, but may exclude things like pickles.