There are a number of nutritional differences between the meat of pasture-raised and feedlot-raised animals. To begin with, meat from grass-fed cattle, sheep, and bison is lower in total fat. If the meat is very lean, it can have one third as much fat as a similar cut from a grain-fed animal.

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Because meat from grass-fed animals is lower in fat than meat from grain-fed animals, it is also lower in calories. (Fat has 9 calories per gram, compared with only 4 calories for protein and carbohydrates. The greater the fat content, the greater the number of calories.) As an example, a 6-ounce steak from a grass-finished steer can have 100 fewer calories than a 6-ounce steak from a grain-fed steer. If you eat a typical amount of beef (66.5 pounds a year), switching to lean grassfed beef will save you 17,733 calories a year—without requiring any willpower or change in your eating habits. If everything else in your diet remains constant, you’ll lose about six pounds a year. If all Americans switched to grassfed meat, our national epidemic of obesity might diminish.

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