The macronutrients — protein, carbohydrates and fat — are nutrients that your body needs in large quantities, and all of them provide a noteworthy amount of energy your body can use as fuel, measured in calories. But of these macronutrients, one of them — fat — provides markedly more energy than the others.
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Carbohydrates and protein both provide 4 calories of energy per gram. But it's fat, gram for gram, that provides the most energy, with a whopping 9 calories per gram.
Which Nutrient Class Provides the Most Calories Per Gram?
When it comes to the macronutrients, the most energy rich of the nutrients is definitely fat. Each gram of fat provides a hefty 9 calories of energy for your body, whereas protein and carbohydrates provide only 4 calories per gram. The difference between 9 calories and 4 calories might not seem that great at first glance, but it adds up very quickly.
Consider this example: If you were to eat a typical 2,000-calorie diet consisting only of protein or carbohydrates, you'd have to consume 500 grams of food to reach that calorie count. If you were to eat a 2,000-calorie diet, very atypically composed only of fat, you'd have to consume a little over 222 grams to reach that calorie count.
Obviously, neither of those diets is actually healthy; you need a certain amount of healthy fats for your body to function. But the example highlights just how quickly calories can add up if you go overboard with your fat intake.
Appropriate Macronutrient Intakes
The recommended calorie intake for a healthy diet varies by age, gender and activity level, as do recommended macronutrient intakes. If your dietary goals are related to a medical condition or elite athletic training, it pays to consult a registered dietician or nutritionist for specific guidance. But for most Americans, the recommended intake ranges in the Dietary Guidelines for Americans, 2015-2020, are exactly the amounts to steer you toward a healthy diet.
Protein should make up 10 to 35 percent of the typical adult's dietary calories. One exception to this is for teenagers and very young adults; for the 14- to 18-year-old set, the Dietary Guidelines for Americans recommends consuming 10 to 30 percent of calories in protein.
Carbohydrates make up a larger portion of a healthy American diet: The recommendation is 45 to 65 percent for adults, including the 14-to-18 age group.
Fats, meanwhile, should make up 20 to 35 percent of your dietary calories if you're older than 18. For those between 14 and 18 years of age, that 5 percent less calories from protein show up in the fat category; according to the Dietary Guidelines for Americans, teens should be consuming 25 to 35 percent of their daily calories in healthy fats.
Read more: 21 Foods That Sound Healthy, But Are Not
Healthy vs. Unhealthy Fats
Healthy fats are necessary for your body to function, but because fat contains 9 calories per gram compared to the 4 calories in protein and carbohydrates, any unhealthy fats you consume can quickly send your calorie intake out of control. So how do you focus on the healthy fats you need?
The answer is as close as the nutrition labels on every packaged food, which break dietary fats down into different categories — saturated, unsaturated and trans fats. Unsaturated fats are generally considered healthful, while saturated and trans fats can be harmful to your body. The Dietary Guidelines for Americans recommends limiting saturated fat intake to less than 10 percent of your daily calories, and ideally you should keep your trans fat intake as close to zero as possible.
What if you aren't eating packaged foods with labels? No problem: Some restaurants make their nutritional information available (although you might need to ask for the nutrition breakdown), and you can use mobile apps or even old-fashioned calorie-count books to look up the nutritional breakdown of most common foods.
Read more: 18 Fat-Rich Foods That Are Good for You
If fats are solid at room temperature, that's a clue that they probably fall into the saturated or trans fat categories.
What About Sugar?
Sugar is classified as a carbohydrate so, just like other types of carbs, you'll get 4 calories per gram of sugar consumed. But that doesn't mean your whole calorie allowance from carbohydrates should come from sugar. In fact, the Dietary Guidelines for Americans recommends limiting your intake of added sugars to less than 10 percent of your daily calories.
But sugar is sneaky. Added sugar is present in 74 percent of packaged foods, according to the University of California San Francisco. Some of the sneaky (and often supposedly "healthy") places it commonly hides include breakfast cereals, snack bars, yogurt, soft drinks and fruit juices.
Read more: 15 Reasons to Kick Sugar
Just like fats, your body needs a certain amount of sugar for optimal function, and you'll find naturally occurring sugars at varying levels in almost any type of food. The key for most people is to avoid added sugars.
For people with diabetes, prediabetes or other conditions that require more attention to blood sugar levels, it's also useful to know the glycemic index of your food, which is a measurement of how quickly it will affect your blood sugar levels.
Practice Calculating Calories From Grams
If you're concerned about how many calories you're taking in, paying attention to nutrition labels or researching the macronutrient breakdown of your favorite foods via mobile apps or calorie-count books is well worth the effort. But while these reference sources usually tell you how many grams of each macronutrient you're getting, they don't always give you the answer in calories as well.
But you can quickly calculate that for yourself, using only the sort of basic math you can do on a smartphone calculator or maybe even in your head.
Because both protein and carbohydrates pack the same amount of energy (4 calories per gram), the calculation to get from grams to calories is the same for both of them. Just multiply the number of grams times 4.
So if you're eating a protein bar that has 10 grams of protein in it, you're getting 10 × 4, or 40, calories from protein. If the same bar has 2 grams of carbohydrates, you're getting 2 × 4, or 8, calories from the carbohydrates in the bar.
For fats, you multiply the number of grams times 9. So if you're eating ice cream that has 22 grams of fat per serving, you're getting 22 × 9, or 198, calories from fat. You can perform the same calculation to see how many calories you're getting from saturated fat or other subcategories. For example, if the ice cream has 14 grams of saturated fat, that would be 14 × 9, or 126, calories.
What About Percentages of Calorie Intake?
So how much of your daily calorie allowance do those amounts represent? To find out, divide the calories in a given food (or meal) by the total calories you take in, then multiply by 100 to convert the answer to a percentage.
For example, if you're a woman between 31 and 50 years old, you might have a recommended dietary intake of 1,800 calories per day. If you eat the aforementioned ice cream with 126 calories of saturated fat in it, what percentage of your daily calorie allowance does that represent?
First, divide: 126 ÷ 1,800 = 0.07.
Next, multiply that answer by 100 to turn it into a percentage:
0.07 × 100 = 7 percent
So that ice cream bar represents 7 percent of your daily calorie intake, which doesn't leave you much more room in this category if you're going to stay below the recommended 10 percent calorie intake from saturated fat — and it illustrates just how quickly calories can add up from the energy-rich nutrient fat.
- Washington State University: Nutrition Basics
- Health.gov: Dietary Guidelines for Americans 2015-2020
- United States Department of Agriculture: How Many Calories Are in One Gram of Fat, Carbohydrate, or Protein?
- Mayo Clinic: Dietary Fats: Know Which Types to Choose
- University of California San Francisco: Hidden in Plain Sight
- Harvard Health Publishing: Glycemic Index for 60+ Foods