It’s time to  end the debate of all debates.

You want to lose weight, gain muscle, and  change your body—but without worrying about whether you’re eating the right  foods. After all, countless diets pronounce that they provide the ultimate  solution to your goals. Only problem is, they all differ in the types of foods  they suggest, the timing of meals, and how much you can eat.

But all  diets are dependent on one common factor: macronutrient composition. That is,  the protein, carbohydrate, and fat content in the foods you eat. Macronutrients  are the single most important factor that determines a diet’s success or  failure. Every diet has its own macronutrient manipulation. On one end of the  continuum are the low-carb diets, such as Atkins and Protein Power (and some  variations of the Paleo Diet). More towards the middle are diets like The Zone  and South Beach. On the other end of the continuum are high-carb/low-fat diets  such as Pritikin and Ornish.

So who’s right? Recent evidence in the  International Journal of Obesity suggests that the diet you can stick to best is  the right one – regardless of the exact breakdown of macronutrients. But this  still leaves questions about how to determine your needs to simplify eating.  Consider this your final answer, and the guide you need to finally determine the  most effective plan for you.

PROTEIN

WHAT IT IS AND WHY YOU NEED IT   Protein is the major structural and functional component of  all cells in your body. Proteins literally play a necessary role in many of the  biological processes that allow you to live and function. Not to mention, about  25 percent of your muscle mass is made up of protein—and the rest is made up of  water and glycogen (your body’s stored form of carbohydrates). So it’s no wonder  why so many diets place a heavy emphasis on protein. But the reason you need to  eat so much is simple: Unlike other nutrients, your body can not assemble  protein by combining other nutrients, so enough must be consumed in your daily  meals in order to achieve your desired health and appearance.

BIGGEST MYTH Despite what you might  have heard, your body can process a lot more protein than you think in each meal. Like a big steak dinner? Don’t worry, you can handle it. The most common  claim is that your body can only handle 20 to 30 grams per meal and that the  rest will go to waste. Nothing could be farther from the truth.

The idea that your body can only handle limited amounts  of protein was one of the initial reasons why people began eating meals every 2  to 3 hours. It was a tactic designed to prevent wasting food, while also raising  your metabolism. However, science has proved that your body can take as much  time as it needs to digest and absorb protein and utilizes all of the nutrients  appropriately. With the exception of a massive protein binge—where you consume  more protein in one meal than your body can handle in an entire day—you can feed  yourself larger doses as part of a healthy approach to your diet.

ADDING PROTEIN TO YOUR DIET  While  most people think that protein is most important before and after your workout,  this isn’t true. Hitting your goal for the day is the most important aspect of  eating protein, whether it’s for fat loss, building muscle, or just maintaining  your weight. Setting your protein goals is a fairly simple process. Research  shows that a range of .5 to 1 gram of protein per pound of body weight is ideal  if you are active. If you want to be even more specific, a good general  guideline is to eat about 1 to 1.5 grams of protein per pound of lean body mass  (LBM). However, most people don’t know or can’t reliably measure their LBM. As  an alternative, consume 1 gram of protein per pound of your goal body weight.

That means if you’re a fluffy 200 pounds and want to be a  lean, toned 180 pounds, simply eat 180 grams of protein per day. Learning what  food intake amounts to 180 grams of protein – or any macronutrient – is a matter  of tracking your intake.

Food journaling software like LIVESTRONG.COM’s MyPlate  can help you record how much protein you’re really eating.

THE BOTTOM LINE The pitfalls of  under-doing protein far outweigh those of overdoing it. Meeting protein  requirements is particularly important when you’re trying to lose weight because  protein is the most muscle-sparing and metabolic macronutrient, and it also  keeps you full.  If you struggle to achieve your protein target through whole  foods like meat, fish, poultry, eggs, legumes, and milk products, you can easily  supplement your diet with protein powder (whey, casein, or egg). There’s no need  to nitpick over the precise distribution and timing of protein throughout the  day, just concentrate on the total for the day, and consume protein at doses and  times that suit your schedule and personal preference.

FAT

WHAT IT IS AND WHY YOU NEED IT    Fat is a major fuel source for your body and has multiple  functions, such as helping your body absorb fat-soluble vitamins, regulating  inflammation, and hormone production. Like protein, fat is considered to be  nutritionally essential because certain fatty acids (linoleic acid &  alpha-linolenic acid) cannot be sufficiently produced by your body for survival,  and thus you must fulfill your needs by eating fatty foods. That’s right. Read  that sentence again: You must eat fat. Although essential fatty acid deficiency  is uncommon among adults in developed countries, the consumption omega-3 fatty  acids is often too low for the purpose of optimizing health and preventing  disease.

BIGGEST MYTH Let’s settle the  score once and for all: Fat does not make you fat.

Once  you get beyond that myth, there are many other misconceptions that could steer  your eating habits in the wrong direction. Most notably, many people still  believe that saturated fat is a dangerous substance that causes heart disease  and should be avoided. This myth has survived for at least the last 3 decades,  and has refused to die despite numerous studies that have shown that saturated  fat is actually good for your body. In a recent invitation-only scientific  consensus meeting, the Department of Nutrition at the University of Copenhagen  determined that saturated fat does not need to be avoided. What’s more, a recent  review failed to find a link between saturated fat and coronary heart disease.  More importantly, it’s not just that saturated fat isn’t bad; the scientists  found that eating saturated fat benefits your health.

That doesn’t mean that all fats are safe. The Dutch  analysis found that excessive trans-fats (from hydrogenated vegetable oils in  shortening, commercial baked goods, and refined snack foods) still pose a  significant threat to your health.

ADD FAT TO YOUR DIET   The best way to prevent heart disease is to simplify your  diet. Eat more whole and minimally refined foods, including an increased  proportion of vegetables, fruits, and nuts—and know how to balance your omega-3  fatty acids. The American Heart Association (AHA) recommends 0.5-1.8 g/day of  combined EPA and DHA, which are omega-3 fatty acids with potent heart-protective  properties. This intake can be achieved by either consuming two to six one-gram  capsules of fish oil, or by having roughly three to six ounces of fatty fish per  day. Vegetarians should realized that achieving the same EPA  and DHA levels  with flaxseed oil is a much less efficient process, requiring roughly double the  dose.

THE BOTTOM LINE Unfortunately,  there isn’t a gold standard for the amount of fat you need in your diet.  Instead, it should be determined on an individual basis. The most recent report  by the Food and Nutrition Board of the Institute of Medicine recommends that you  eat at least 20 to 35 percent of your total calories from fat. But realize that  eating slightly more than this won’t cause added fat storage as long as your  total calories match your goal for weight gain, loss or maintenance. If you  still want a target, divide your weight in half and eat that many grams of fat.  So if you’re 180 pounds, you would aim to consume 90 grams of fat per day.

CARBOHYDRATES

WHAT IT IS AND WHY YOU NEED IT   Carbohydrates have many functions, but their main role is to  provide energy to the cells in your body. Carbohydrates are unique because they  are not considered essential. That’s because your body can synthesize its needs  from non-carbohydrate sources though processes called gluconeogenesis and  ketogenesis. As a result, the other foods you eat (proteins and fats) can be  converted into energy, meaning that your general survival does not depending on  eating carbohydrates. As mentioned before, this can’t be said about amino acids  (protein) or essential fatty acids (fat)—both of which you need to obtain from  foods.

Still, while carbohydrates technically are not  essential, you do need them when living an active lifestyle. Not to mention,  fruits and vegetables are two of the most important sources of carbohydrates,  and both provide nutrient-rich calories that protect against disease.

BIGGEST MYTH Carbs do not make you fat.  (Picking up on a theme?)

Ever since the low-carb craze  began in the early 1990s, carbohydrates have been demonized as the cause of the  growing obesity rates. And while a low-carb diet does have many health benefits  and can lead to lasting weight loss, there is no “metabolic advantage” to going  low carb. In fact, a study published in the American Journal of Clinical  Nutrition compared a low-carb diet with one that was higher in carbohydrates.  The result: There was no difference in weight loss or changes in the ratio of  muscle-to-fat. What’s more, when researchers compared a low-carb diet with a  low-fat diet (and higher in carbs), they discovered that neither was better at  boosting metabolism.
You can analyze studies and research  all day, but the bottom line is simple: You can eat carbs and still lose weight.  The diet you choose will be largely dependent on many personal preferences and  eating styles, and whether it’s low carb or higher in carbs, both strategies can  be equally effective at creating change.

ADD CARBS TO  YOUR DIET Generally speaking, if you’re active you need  anywhere between one to three grams of carbohydrate per pound of lean body mass.  The carbohydrate requirement tends to range more widely than the other  macronutrients because it’s largely dictated by how many calories you’re trying  to eat per day, and your total amount of activity. In other words, determining  the right amount of carbs is really the fourth step in your diet plan. First,  figure out how many calories you need, then set goals for proteins and fats.  Once you establish those guidelines, then your remaining calories for your  weight goal should be filled in with carbs.

THE BOTTOM  LINE Carbohydrates, just like fat and protein allotments,  should be comprised mostly of whole and minimally processed foods. For most  people, carbohydrates are a form of dessert. And if you’re eating healthy, about  10 to 20 percent of your total calories can basically come from any foods you  want. Your choices among carb-dominant foods (fruit, milk, starchy vegetables,  non-starchy vegetables, grains, legumes) should be based on your personal  preference and tolerance, while maintaining as much variety as reasonably  possible. As a rule of thumb, eating two to three fruits and two to three  vegetables per day will usually fill up the majority of your carbohydrate  allotment, while providing beneficial nutrients that will help your overall  health.  Easy enough, right?