Any diet can be healthy in the short-term, particularly if it is causing fat loss and resolving obesity. Given the massive negative impact that excess body fat has on your health, any diet that takes you from an obese body composition to a normal body composition will very likely have a net beneficial impact on your health.
But just because a weight loss diet improves your health, does not mean that it is a healthy diet to follow for a long period of time.
Consider type 2 diabetes, for example, which is caused primarily by surpassing your personal fat threshold. If you follow any diet that causes fat loss, we know that type 2 diabetes can be cured once enough body fat is lost to get below your personal fat threshold and remove fat from the liver and pancreas. Curing diabetes is one of the most important things you can do for your health if you currently have type 2 diabetes. It supersedes pretty much everything else.
Yet, let’s say you use a carnivore diet to accomplish that goal. Great! You found a diet that let you lose body fat and vastly improve your health. But over the long-term, you are exponentially increasing your risk for colorectal cancer and other health problems due to the dysbiosis caused by a lack of prebiotic fiber while eating a carnivore diet.
So, when using a diet to accomplish a specific goal, remember that it may not be the diet you use after the goal is achieved.
While there are many variations of what a healthy diet looks like, they all tend to center around an abundance of fibrous vegetables and fruits, unsaturated fats (as opposed to saturated), and adequate protein from lean animal foods (ideally seafood or poultry) or protein powders (especially for vegans). And don’t stress about it. Try to stick to this framework, but don’t be neurotic about it.