How Is Milk Fat Calculated?

Cows produce milk to nurture their young.

Cows produce milk to nurture their young.

Cow’s milk is nature’s perfect food for growing a baby calf into a mature cow. Just as human babies require a higher percentage of calories from fat than adults for growth and development, baby calves also need a substantial amount of fat. You may be surprised to know that your glass of milk may contain more fat than does a body good.

A Weighty Issue

The amount of fat in milk is quantified based on weight. That is, instead of describing the percentage of calories from fat in the milk, 2-percent milk means that the fluid contains 2 percent fat by weight. Using a nutrient-to-weight ratio disguises the true amount of fat in the milk. This approach is also used to describe the amount of fat in other low- and reduced-fat dairy products, such as cheese and yogurt, leading you to believe that these products are healthier than they really are.

Full-Fat Milk

To provide for the baby calf, whole milk is a rich source of calories and fat. One cup of whole milk weighs 244 grams and contains 149 calories and 7.93 grams of fat. To calculate the percent of fat by weight, divide the grams of fat by the total weight and then multiply by 100 -- or 7.93 / 244 X 100 = 3.25. Whole milk could technically be sold as 3.25-percent-fat milk, which would lead you to believe that it is low in fat. In reality, 1 cup of whole milk actually provides 48 percent of total calories from fat. To calculate this, divide 71 calories from fat -- each gram of fat has 9 calories -- by 149 total calories and then multiply by 100 to get 48 percent.

Amount of Fat in 2-Percent Milk

Though 2-percent milk is marketed as a healthy low-fat food, you may be getting more fat than you bargained for. One cup of 2-percent milk weighs 244 grams and contains 122 calories and 4.8 grams of fat. This equates to 2 percent fat by weight, with the other 98 percent coming mainly from water plus some carbohydrate and protein. However, as a percentage of calories, 2-percent milk really provides 35 percent of total calories from fat, which does not meet labeling requirements for a low-fat food.

The Skinny on Skim Milk

Most people believe that skim milk contains no fat. In fact, 1 cup of skim milk weighs 247 grams and contains 86 calories and 0.44 gram of fat. If you crunch the numbers, you will see that skim milk is less than 0.5 percent fat by weight and 4.6 percent fat as a percentage of total calories. Clearly, it is the best option if you choose to drink cow's milk. For comparison’s sake, soy milk is 1.2 percent fat by weight and 30 percent fat by percentage of calories, almond milk is 1 percent fat by weight and 75 percent fat by percentage of calories and rice milk is 1 percent fat by weight and 18.6 percent fat by percentage of calories.

 

References

About the Author

Tara Martine is a registered dietitian and licensed dietitian/nutritionist based in North Carolina. She specializes in sports nutrition, plant-based nutrition and weight loss. Martine holds a Master of Science in nutrition from the University of North Carolina at Greensboro.

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