If you're hear reading this it's because your interesting in the diet philosophy of eating according to your macro needs. Macro is short for macro nutrient, which refers to the three main constituents of food:
In it's purest form, dieting according If It Fits Your Macros (IIFYM) doesn't take into account eating 'healthy'. The sole purpose of macro dieting is to hit your macros and target calories without being concerned where those macros and calories come from. It's certainly possible to put a healthy spin on an IIFYM diet, however, simply by choosing healthy macro sources.
In this context, 'diet' is used to refer to a style or way of eating, not necessarily restricting calories. Although a macro based diet can be used to lose weight, it can just as easily be used to maintain current weight or to add weight in the case of a bulk. With a focus on calories and getting enough protein and fat, macro based dieting makes it easy to achieve your weight loss, gain, or maintenance goals.
For a long time, bodybuilders preached the mantra of "eating clean" in order to get gains or to cut fat. But a diet of chicken, rice, tuna, broccoli, protein shakes and other "bland healthy food" can get pretty boring over time. Some fitness professionals began to focus on calories and protein and found that contrary to what they thought, it didn't seem to have an adverse impact on their body composition. The soon discovered that as long as they hit their goals, they continued to make progress. And it didn't matter where the calories, protein, fats and carbohydrates come from.
When people first starting looking at controlling their weight, the firth thing they usually think of is "cleaning up" their diet. This means getting rid of many of the foods people enjoy: fried chicken, pizza, sweets, fast food.... these things had to go. But while there can be a connection between what you eat and your health, when it comes to weight control, the connection is much more nebulous. Weight control is all about calories in and calories out, regardless of where those calories come from.
"Eating clean" can certainly help with weight loss, simply because "eating clean" eliminates the source of many calorie dense foods: candy, sugar, white bread, etc. Of course cutting out these types of foods resulted in weight loss, imply because less calories were being consumed. So a connection between cleaning up your diet and weight loss became ingrained in the public's mind.
Almost everyone knows the more you eat, the fatter you get, unless you are doing an unholy amount of exercise to burn off the calories, like Michael Phelps swimming for 6-8 hours a day. Along those same lines, since "crap" food tends to be very calorie dense due to an excess of fat and sugar, the more crap food you eat, the quicker and fatter you get.
Let's say you use 2,000 calories a day. Unless you have a medical condition, like hormone imbalance, thyroid problem, or some other disease or disorder, if you eat 2,000 calories a day, your weight will stay the same. If you eat more than 2,000 calories a day, you will gain weight, and if you eat less you will lose it. Likewise, if you eat 2,000 a day and burn 100 calories through exercise, you will also lose weight.
What macro based dieting does is break down your calories into the best proportions of protein, fat and carbohydrates. What that means is that as long as you track these macros, it doesn't matter where you get them, as long as you stay at your caloric goal for the day.
So this means you can eat the foods you love, as long as you don't exceed your daily caloric limit. It also means that you have to track what you eat, because how else will you know if you are meeting your macros?
There are a two things you need to do when heading into macro based dieting:
Once you have these numbers, it's simply a matter of adding up what you eat to hit those targets. There's only one question you need to ask yourself before you eat something: Does it fit your macros? If the answer is yes, then have at it!