I would say that most people who use those phrases have no real idea of what they really mean. The first comes in when people are discussing food groups that have been declared by the 'annointed' to be healthy inclusions in our daily living. The second usually gets thrown in when one person suggests to another that a particular food item liked by the latter is unhealthy.
Yet the 'annointed' appear to be failing when it comes to maintaining public health. Every proclamation to eat 'this' food or 'that' food and reject 'these' foods, seems to coincide with the beginning of a new epidemic of diabesity.
Surely it cannot be that hard to determine what foods our body needs and in what proportions. After all, we have been doing it (as has the rest of the animal kingdom), without effort for most of the last two and a half million years. When did it all start going wrong?
We know that our body needs certain amino acids and fatty acids that MUST be obtained from our food. (If we don't get them then we fail to thrive, get sick and eventually die.) As well as these, it has been determined that deficiencies in some minerals and vitamins will, likewise, cause us health problems. We even know what the amino acids and fatty acids are - phenylalanine, valine, threonine, tryptophan, methionine, leucine, isoleucine, lysine, and histidine (for the amino acids) - alphalinoleic (an omega 3 fatty acid) and linoleic (an omega 6 fatty acid), (for the fatty acids). The rest can be made in our body - unless we have a pathophysiological condition which prevents prevents this. Further complicating the issue is the interaction of the omega 6 and omega 3 - if you don't have them in the right proportions you can get problems. (One is inflammatory and the other anti-inflammatory).
So what is the problem, surely we can just bundle this stuff up and eat it? Et voilà! - Healthy outcome? Certainly our food must have come naturally bundled up like this prior to the supermarkets or we would never have survived evolution.
When we look at the last hundred thousand years, we notice that our brains peaked in size about 90,000 years ago. They remained a constant size for another 60,000 years. They reduced in size by about 3% over the next 20,000 years. Over the remaining 10,000 years, until now, they have reduced by a further 8% - that is an 11% reduction over the last 30,000 years. The major change in our history over that period has been the move from a hunter gatherer to an agrarian way of life. Similarly, our bodies have reduced in stature and we have developed tooth decay over this same period. Modern hunter gatherer societies that have been discovered and colonized over the last few hundred years, have all had people of healthier stature and dental health than that of the agrarian colonizers of the time. This has quickly changed however as the colonized peoples have changed to the agrarian ways of the colonizers.
One plausible explanation is that agrarian practices have moved our societies to more of a plant-based diet than that of our ancestors. It has been found that deficiency of vitamin B12 contributes to reduced stature and brain size. In modern studies it is found that vegetarians have smaller brains than meat eaters. Vitamin B12 can only be obtained naturally by eating meat products or by reintroducing some of our own stools back into our food cycle - this can be achieved by growing vegetables in human manure and not completely washing it off before eating.
Other important minerals that we need, calcium, magnesium, iron, copper, zinc, potassium, sodium etc. can be obtained through plants and fortified plant-based foods. Unfortunately, natural chemicals, (phytonutrients), also found in the plants can also block absorption of many of these minerals by the human body. The reason being that they form strong bonds with the divalent ions of the minerals - meaning they pass through us without being absorbed. These phytonutrients in plants are part of their self-protection mechanism, unlike animals, they cannot run away or fight potential predators with their teeth and claws, so they make themselves unattractive as food by robbing us of the nutrients contained in them. While our early ancestors found this out and moved to more efficient foods, our more recent ancestors have spent time trying to make them more edible, by fermenting, cooking, selective breeding and nowadays, genetic modification. We have also developed, (naturally), bacteria in our gut and certain chemicals like amylase (via the genetic mutation AMY1) that help us digest some of the plants. Constant exposure has caused our own genetic selection to help deal with our agrarian change. Nevertheless, our health has still maintained in decline over the last 20,000 years.
Balanced diet for some animals, like gorillas, seems to be an assortment of fruit and leaves. Their large hind-gut allows the bacteria they store to convert much of the material they eat into fatty acids - which in turn provide 60%-70% of their daily fuel needs. The case is similar with fore-gut digesters, like ruminants. Humans have not yet evolved such a gut so we cannot get our energy needs met by turning plants into fatty acids through the good offices of bacteria. While we CAN meet our energy requirements by eating plants, it has to be by focusing on sugars from fruits, starches or basically carbohydrates. However, this is where the balance goes 'off' for us. If we eat sufficient carbohydrates to meet our energy needs, we do not get enough of the amino and fatty acids, as well as minerals and vitamins, to rebuild our dying cells. We become nutrient deficient. If we eat enough carbohydrates to meet our nutrient deficiencies, then we eat too much energy and cannot expend it - so we store it. That, then, is the choice - we get enough nutrients and get fat - or we stay thin and get sick. Either way we get sick.
It might be possible to engineer a 'balanced' diet from plants - but so far it seems that no-one has found one that is uncomplicated, palatable or sustainable.
Meat from animals, as food for humans, seems much easier to formulate into a balanced diet. It turns out that if we consume a plant-eater, like a buffalo or an antelope, nose-to-tail, we can get just the right amount of energy in the right mixtures of fatty and amino acids - with a few vitamins and minerals thrown in for good measure. Furthermore, if we restrict ourselves to a diet that is only animal in nature, then we don't get overly fat - it seems we somehow find ourselves replete without putting on extra weight. This suggests that our body's metabolism has met all of its nutritional needs and does not give us a craving for any food that contains some 'missing' nutrients.