Hard to argue with. Exactly what constitutes a healthy diet, though? It's worth asking, surely?
The problem with such a question is that once you've answered it, you've also defined what makes an "unhealthy" diet. That is... "here's what makes for a healthy diet, therefore anything else is unhealthy". That's how most people seem to think, from my observation. It is problematic.
The tendency I've noticed is to think of a list of all the things that are probably a good idea, and then if you're not doing all of them you have an unhealthy diet. And the logic continues that if you have an unhealthy diet, you'll not be successful in your weight loss or body condition goals. This is highly problematic.
So let's start at the opposite end of the issue, and discuss what would make for an unhealthy diet. It stands to reason that if we can define "unhealthy", anything else is quite suitable for good health and good results from training.
An unhealthy diet would be deficient in important vitamins and minerals.
This is important for good health in general, more than for weight management or performance and results at training. I had to double check this point with a client of mine who happens to be qualified as a Diet Tech (yeah that's right) to be sure, but generally speaking as long as you get your five (or more) serves of fruit and vegetables per day, you're not likely to be deficient in any micronutrients.
Especially if you eat a variety of different types, different colours ("eat the rainbow", as the saying goes) you're going to get a pretty good spread of vitamins and minerals. More's better, but 5 serves a day will do.
So that part is pretty simple.
An unhealthy diet would be excessive in calorific intake.
This is the obvious one. Now... depending on who you listen to and which blogs you read you'll be told that only carbohydrates are the problem, or only fats are the problem, or only certain types of one or the other from certain sources are a problem. That's all horse shit. Excess calories are excess calories, regardless of where they come from. If you consume more than your body has a use for, it will be stored as fat.
Now... it's normal and perfectly healthy to be carrying a certain percentage of body fat within a certain range depending on if you're a man or woman. Excessive body fat though... we all know it's not healthy whether we want to face up to that or not. There are host of other symptoms that are associated with excessive intake, clogged arteries, heart disease, inflammation and so on... people like to argue about which source of calories is responsible, but this is missing the point entirely. The issue is that we are in excess of our requirements, not the source of the excess calories. Regardless of the source, if we were not in excess there would be no issue as the body would find something productive to do with these energy resources.
So, rather than worrying about which food choices are healthy or unhealthy, simply focus on not being in excess of your requirements. However...
A diet that is of an insufficient total calorific intake would also be unhealthy.
As explained above, we don't want to be in the habit of regularly consuming in excess of our energy requirements. But with that being said, energy is still an important resource that we require for good health. Especially in active people who are trying to create a lean and athletic body condition through hard and strategic training, to be insufficient in energy intake can mean that all of that training is actually to the detriment of your physical health.
It is somewhat baffling to me that so many people in the industry or just fitness enthusiasts believe that the way to achieve great results from training is by depriving the body of an important resource, usually carbohydrates but quite often just "all" forms of intake. It is not enough simply to meet your micronutrient requirements, or even your protein requirements. A diet that does not provide sufficient energy to maintain a healthy body weight while accounting for the type and amount of activity your participate in is unhealthy.
An unhealthy diet would be rigid and inflexible, with no regard for your psychological needs.
We're designed to enjoy food. Even within a fine tuned nutritional plan designed to produce elite level performance and results from training, there should be a focus on meeting those requirements from choices of foods that you enjoy and will look forward to eating, rather than on choices that don't enjoy but are "good for you". There should even be room for some choices purely for indulgence.
Rigid diet plans that ban any indulgent choices, that are based on will power and discipline, that imagine that your body treats calories from more enjoyable sources differently to ones from more "virtuous" sources, and leads to feelings of guilt or failure associated with the perfectly natural human behaviour of enjoying food, is clearly unhealthy and an entirely irresponsible thing to promote.
So, what then would a healthy diet mean?
Get your five or more serves of fruit and vegetables, get enough protein, enough dietary fats, enough carbohydrates and fiber, enough total energy intake, but not too much. Boom you have a healthy diet.
Oh and all this talk about it being too expensive to eat healthy? It’s as expensive as your tastes dictate. That’s all.