Is It Good For Me? How to Know For Sure

Instant gratification is a powerful expectation. Once we become accustomed to it, it can define the value of something, just by giving us that initial, endorphin-filled feeling of "now I have it!"
When it comes to fitness and nutrition, though, this "instinct" can hold us back. There are no quick fixes to becoming healthy, losing weight, or gaining muscle.
Every week, another product appears on the market whose claims of being "what you need" to reach your goals sweeps the nutrition field: apple cider vinegar, coconut oil, kale, açaí, goji berries, garcinia cambogia, white grapefruit, paleo and other low-carb diets, et cetera.
But none of these products or routes is "THE" answer. The actual answer is not to make one or two or three changes while keeping everything else the same. It is, instead, to transition into a healthy lifestyle wherein your health and longevity play a key role in your decision-making. The questions of "is this [food or activity] healthy?" and "will this [food or activity] positively contribute to my health and fitness goals?" should constitute a significant portion of your daily conscious thinking, and active measures to accomplish these ends should constitute a significant part of your daily conscious action.
This is, of course, dependent on having fitness goals. So you must be empowered to think knowledgeably in order to set them, and to act confidently on that knowledge in order to meet them.
This transition is easier for some people than it is for other people. It has a lot to do with your current level of health, your day-to-day schedule, your mentalities, your upbringing, and your relationship (or lack thereof) with physical exercise. Just changing from little or no conscious thought about fitness to some conscious thought about it is a challenge for many people, never mind reaching the point where it is regularly considered and acted upon on a daily basis.
Part of the reason for this is the perceived "learning curve." All of our lives, we are told to become educated in our field of study and profession in order to get ahead in those fields. But rarely are we told to, "educate yourself on maintaining good cardiorespiratory health!" "Learn about retaining insulin sensitivity!" "Develop a firm grasp on how antioxidants CAN EXTEND YOUR LIFE AND FIGHT DISEASE!"
Gym class is of little help. Now, I'm not trying to blame Phys Ed. teachers here, but gym class should be about more than either learning how to play floor hockey, or learning how to get out of playing floor hockey. It should be about learning why floor hockey or any other physical activity is important to your life, and if you don't like floor hockey, here's a bazillion other options to choose from.
Similarly, we aren't told much about the value of nutrient-dense food over nutrient-deficient food, at least not before college. The roles of protein, carbohydrates, fats, and fiber are barely understood by the general populace. Rarely do we hear about the law of thermogenics in relation to health: "if calorie intake exceeds calorie expenditure, you will gain weight. If caloric expenditure exceeds caloric intake, you will lose weight." How many times did you hear about how awful heart disease, cancer, diabetes, and hypertension are, without being told how to prevent them besides "eat your vegetables"?
Like I said, different people learned about these subjects differently, so maybe you learned about them just fine, and maybe you are doing just fine with your fitness level right now (I hope). But many people's understanding of them is deficient; even if they are excellent at building a house, balancing a budget, writing a novel, or raising a child, staying and feeling healthy is something they just can't seem to nail down.
There are so many voices in the media and everywhere telling us to do a million different things in order to "get fit." Healthy, "fit" people seem to have mastered these million things, while everyone else is still struggling. Those who were brought up to have a positive relationship to physical exercise have an advantage, and everyone else has a disadvantage. In neither case, of being "born into" healthy habits or overcoming unhealthy ones and embracing a healthy lifestyle, does it occur overnight. And keep in mind, you can't always tell how healthy a person is by looking at them.
The "secret" that many successfully healthy people have learned is what I am right about to share with you. The three criteria for knowing whether something---a food or an activity---is good for you, are the following:
1. Does it fall within my health restrictions, if any, caused by a medical condition such as lactose-intolerance, Celiac's disease, Crohn's disease, or high cholesterol? If so, do not eat it.
2. Is it aligned with my sense of ethics? You should not eat anything that you don't approve of, ethically. Avoiding moral compromises helps to reinforce feelings of self-control, discipline, and long-term thinking, and produce an "eating to live" mentality, rather than a "living to eat" mentality.
3. Does it fit my fitness goals? If you want to run marathons, you will need carbohydrates in your diet. If you want that "dry, shredded look," carbs are a no-no. The health value of any food is almost completely dependent on what you are trying to achieve. Of course, reaching your daily intake goal for fats could be achieved by eating bacon, or by eating avocado, and I would be hard-pressed not to say that one is healthier than the other, especially if one of your fitness goals is longevity.
Another simple criterion you could consider in deciding if a food is good for you is its nutritional content. If it is rich in nutrients, it is good for you. If it isn't, or if it is also rich in bad things like saturated fat, cholesterol, or added sugar, it is bad for you or should at least be eaten in moderation.

The majority of your foods should be nutrient-dense, whole food (unprocessed or minimally processed) options that leave as little question of their nutritional value as possible. Nutrient-dense whole foods have many benefits: they keep us feeling full longer due to higher fiber content. They give us more sustained energy because they are more vitamin-rich and their carbohydrates are broken down more slowly. Due to that increased energy, they complement our exercise routines. And, they contain more water to help us stay hydrated and reduce water retention ("water weight").
The trick to remember, no matter how "healthy" all of your foods are, is that law of thermodynamics: "if caloric intake exceeds caloric expenditure, you will gain weight. If caloric expenditure exceeds caloric intake, you will lose weight." So if you did nothing but "eat your vegetables" for 3000 calories a day, there's a good chance you'd gain weight.
That's because there is no "quick fix," whereby "you do this and ONLY this, and all of your health worries will be solved." No. The marketing value of such products is that, once you've implemented them, they free you from the burden of having to think about health and fitness, or change anything else about your life.
The truth is, health and fitness require sustained informed thought and decisionmaking, and conscious choice. In other words, it requires some thinking and some time out of your life to really make it happen. But isn't your health worth it? Wouldn't it feel good to know that your decisions are based on achieving a larger purpose, and the stress of "not knowing what you're doing" can be replaced with the empowered feeling of being a nutritional badass?
Now, another question is, do these criteria reduce food and exercise to mere instruments for larger goals, alienating them from their individual pleasurable attributes? Do they demystify flavor and apply a utilitarian purpose to every macro- and micronutrient? Do they encourage every food-related decision to be considered and thought about and monitored, and thereby remove the joy of eating?
I would say no, they don't. What they do is repurpose food to suit a greater purpose than the hunger or flavor of the moment. Hunger and flavor are indeed important, and needn't be left behind. But the stress and destructive cycles that mindless, uninformed, or confused consumption can cause should indeed be left behind immediately. There is a very clear pleasure and reward to eating and living with your health being an end result. It is its own reward.
Plus: kale, watercress, avocado, pistachios, chickpeas, arugula, pineapple, kiwi, black beans, oatmeal with ground flaxseed and agave, baked sweet potato, and a million other things are delicious! But, like floor hockey, health is an acquired taste. All it takes is learning how to skate in a straight line, and you're 100% closer to success than you were before.