Nowadays, the term "healthy" is meaningless. Anybody can say so-and-so is healthy without really going into depth in the presumptive health benefits.
I used to be one extremely impressionable person. I can watch any documentary and believe every word the documentary says. I watched a documentary about what would happen to the end of the universe and really believed in the "Big Freeze". I watched documentaries and film series on religion. Same thing. I started believing that someone named God existed, and that the Bible was God's word. All those documentaries were so convincing to me at the time that I started believing that Jesus was the messiah, that the Bible pointed towards him, that Jesus was crucified, and that Jesus resurrected himself.
I watched a fake documentary about a teenage girl who was bullied in school. I believed it fervently and thought the sob story was true. As I later read the Internet Movie Database official webpage, I found out that all the characters were actors, and the school was completely fake. I once watched a documentary about cattle farming in the United States, which turned out to be propaganda for veganism. I discussed the issue with Dad, arguing that we should go vegan. Dad humorously told me that if we as a family go vegan, then the price of meat would drop, and other families would eat more meat. Then, I thought he did have a point. If we as a family did go vegan, then we would be missing out on our nutrition, and we still will not help the planet, because it's us versus the billions of other people on the planet. Although I believe that humans should be good stewards of the Earth, I also believe that veganism is not a practical solution.
When I was little, I was taught in school that skim milk or low-fat milk was preferable over whole milk, and that whole milk should be reserved for babies. Now, some "health experts" say that 2% low-fat milk or whole milk is preferable over 1% low-fat or skim milk, because of the fat content. Eh? For that reason, I don't care what milk I drink. I still don't drink a lot of milk, because I know milk tends to give me a stomachache afterwards and sometimes a case of diarrhea. Besides, I can get my vitamin D and calcium from fish, eggs, and spinach. I used to drink more milk when I was in primary school, but that was because the school offered it as part of the meal plan.
Then, there is sugar. I watched several documentaries that talked about how bad sugar was, and that eating too much sugar was bad for health. They always used fast food as the straw man. Fast food is an easy target, because it is pretty obvious that it is bad for health in so many ways. But it's still a straw man argument, because the documentaries are essentially being anti-fast food/anti-processed food/anti-too many calories, not anti-sugar.
Let's do a little thought experiment here. Suppose a healthy person is told to eat nothing but strawberries all day. He can eat strawberries as much as he wants, any time he wants, but he can ONLY eat strawberries. Strawberries seem very healthy, right? So, let's force this person to eat a lot of strawberries and see what happens! Do you really think that the healthy person will stay healthy on a strawberry-only diet? Or do you think that the person will become severely malnourished?
Then, there are the fad diets -- low-carb diet, low-fat diet, plant-based diet, Atkins diet, Paleo diet, Jenny Craig diet, NutriSystem diet, et cetera. You know what? My relatives have always eaten a high-carbohydrate diet -- a big bowl of white rice and vegetables every day, and they have always been slim. In addition, people nowadays would suggest brown rice or quinoa over white rice. No, I don't think it's any better than white rice. White rice may not have the fiber or the nutrients, but it is usually eaten WITH the vegetables, which contain fiber and nutrients. And white rice is more absorbable and has a longer shelf life than brown rice. Therefore, white rice is the more economical, better choice.
For low-fat foods, I usually see them with labels that say "low-fat". But really, there are many foods that do not have labels like that. Grains are never labelled as low-fat. Fruits and vegetables are never labelled as low-fat. Usually milk and dairy products and things that contain dairy products somewhere in the ingredients are labelled as low-fat. I have never seen meat and eggs labelled as low-fat. So, the low-fat labels typically go on foods that I don't eat regularly in the first place. For me, this is the most useless health advice ever.
Then, there are the plant-based diet (veganism and vegetarianism) and the meat-based diet (Atkins and Paleo diets). The health claims promoted by supporters of the Atkins or Paleo diets directly contradict the health-claims promoted by supporters of veganism and vegetarianism, and both sides say they promote health and well-being. First of all, I don't know anybody who just eats animal fat, and I don't think lean meats are more preferable than so-called "fatty meats". If someone happens to buy "fatty meats", then he can just cut off the fat and use it as fresh cooking oil, and if the fat comes from a pig, it's called lard. The muscle meat of the animal would be shared by others at the table and eaten.
Second of all, I once wandered casually into the Frozen Foods section at the supermarket and gazed at the frozen dinner selections. Among them were Atkins-label TV dinner meals. They were considerably more expensive than the other frozen dinner meals, and the meal presentation on the cover looked about the same as the cheaper frozen dinner meals. The Atkins-label packaged food can also be found near the Pharmacy section at Walmart, and it's shelved right next to NutriSystem and Jenny Craig and vitamin tablets. They may cost anywhere from $5 a container to $10 a container to even $50 for the whole package. What a waste of money. I can buy $5.00 worth of bunch spinach ($0.99 a bunch, typical price), and that's enough food for a family of three for a week. When bunch spinach goes on sale, the purchasing power can increase by a twofold.
As for the advocates of veganism and vegetarianism, I don't trust them either. Although veganism/vegetarianism is a deliberate ethical choice, and indeed Buddhist monks would strictly eat vegetarian meals because of values of ascetic living and meat is traditionally regarded as luxurious, veganism and vegetarianism aren't necessarily healthy. You can eat nothing but doughnuts and coffee, be a normal-weight person, and still be incredibly nutrient-deficient. Death is highly likely with severe nutrient deficiencies. I know this stuff, because I have taken a collegiate course in hemotology and a course in medical dietetics. Normal cells should look consistent and kind of boring. The more interesting and beautiful a cell is, the more likely the cell is malignant or indicative of a dysfunction/disorder. Both genetics and the environment play a role in the health of the cells.
Fast food always receives the most blame for just about every kind of health problem in the book. But then, people who frequently eat fast food tend to buy huge amounts of fast food for themselves. One person, one meal. People on a strict budget can order something from the Dollar Menu, but the intent is still eating one item for one person's mouth. A poor family of four can save money by buying a single burger on the Dollar menu and dividing the burger into four pieces with a knife and collecting some tap water from the water fountain. Fruit cup and raw vegetables are also on the Dollar Menu. Maybe the family can forage for wild dandelions and cook them for dinner. The milk bottle is on the Dollar menu, but it costs as much as the burger.
So, it may be purchased monthly, while water from the fountain will be drunk every day. Because the milk is considered the luxury product due to the relative high price on the menu, the milk can be rationed and diluted, instead of drunk in one mealtime by one person. I once observed a highly unusual eating style of a McDonalds burger meal. The family probably didn't frequent at McDonalds, so at home, the members would put the burgers on plates and eat with chopsticks. The chopsticks would grab the top bun first, then the vegetable toppings, then the burger patty, and finally the bottom bun.
I personally know someone who was at the time reading a book about health. She showed the book to me and said that the book "promoted health". But then she added a witty remark, "I really don't know what to believe anymore." In retrospect, I think that she definitely sums up my sentiments about all the health claims. I still want to eat a healthy, balanced diet, though. So, who should I turn to now? Well, like the Christians who created the "What would Jesus do?" movement, I decided to ask the question, "What would Mom do?" or "What would Grandma do?"
My mother would always serve home-cooked meals, many of which were from her own childhood. She would eat rice and vegetables every single day, at almost every single mealtime. Because of the price and scarcity of meat in the diet, my mother grew up as a very thin girl, and she never liked being so thin. No one liked being thin. Even on my Dad's side of the family, Dad and his young friends would compare how fat they were, because fatness was a sign that a family could afford luxury goods (in their case, meat and spices were highly luxurious). But the problem was, nobody could really get fat, even if they wanted to.
In order to gain just one pound per week of fat, one has to increase the amount of calories, and the increased amount of calories correlates to the amount of food one has to eat and the amount of money one has to spend to buy the food and the amount of food that can possibly fit inside one's stomach before one feels uncomfortably full and vomit involuntarily. As you can see, getting fat was extremely difficult to achieve, when you add in the fact that you have to spend calories to keep your body alive and spend calories on daily physical activities (walking and cycling as a means of transportation).
Obviously, I eat differently than my parents when they were younger. I have access to any type of food year-round. But the basic, cultural diet plan is still a bowl of rice and some vegetables/meats. Any other type of food (i.e. ice cream, chips, crackers, cookies, free samples at the grocery store) does not make a meal; they are recognized as snacks, and snacks should be scrutinized and moderated, because snacks are luxurious add-ons to the basic backbone. Eating out should only occur, if you have a special guest/visitor at your house or if you are on vacation or if you want to celebrate an event.
I don't expect and I wouldn't advise other people to follow my diet. What works for me may not work for everyone. For example, I know Northern Europeans tend to consume a lot of milk and dairy products, because they can digest lactose during adulthood, whereas most people around the world are lactose-intolerant to some degree. Expecting a lactose-intolerant person to drink milk because you think it helps build bones is NOT healthy, practical, and ethical.
And buying fortified milk substitutes may not be affordable or economical, when calcium and vitamin D can be extracted from other and much cheaper foods. I remember learning about a "disorder" in hematology class, called hereditary hemochromatosis, but I think of it as more of a maladaptive trait in modern Western society, where most iron is derived from meat sources. The instructor would explain how people only brought meat to the dinner table once a month or so, and people who could absorb the iron readily were less likely to have iron deficiency than their "normal" counterparts, so the trait was not a problem.
It is important to understand that biological fitness is how well an organism can adapt to the environmental conditions. When the environment changes, different traits will be selected for and be selected against. There are no good genes or bad genes; there are only a variety of different genes, and some genes just happen to work with a set of conditions. In addition to biology, culture plays a big role in diet. Jews can only eat kosher food, and Muslims can only eat halal food. Religious and biological dietary restrictions do exist and matter in food choice. I think "eating healthy" is just trying to get to know your body within your cultural background.