The Truth About Calories

If you can’t even remember a time before the word “calorie” was consistently on your radar, it’s for good reason. And, not just because everywhere you look it’s “no calorie” this and “low-cal” that. Americans have been preoccupied by this little number for more than a hundred years. Since “scientific eating” trends came into vogue in the late 19th century, the ability to quantify aspects of the food we eat has been something of an obsession: Don’t we all want a simple formula for keeping track of how “good” or “bad” our diets are? In fact, there was even a 1923 romance novel, Outside Inn, that prominently featured calorie counting and nutritional science as themes. Yes, you read that right — two smitten love birds engaged in a sexy repartee about...calories.

If you’ve ever fallen prey to a strict calorie-counting diet, you’re likely to see those numbers as something much more nefarious than what they actually are — simply a unit of measurement that expresses the amount of energy your body can extract from a food. (Actually, a true calorie is a really small measure of energy. The unit of measurement commonly read on food labels is normally a kilocalorie, or 1000 calories.) Unfortunately, determining what foods (and how much of them) you should eat isn’t really as easy as some caloric arithmetic, because, as we all know by now, not all calories are created equal.

As a rule, different types of foods contain different numbers of calories. A gram of fat has nine calories; a gram of either protein or carbohydrates contains four calories. So, if you’re trying to cut down on calories — to lose or maintain your weight — you should just cut back on fats, right? Not so fast.

In recent years, the tides have turned away from the simplistic “calories in versus calories out” approach to weight loss. In 2011, a long-term follow-up study involving more than 120,000 non-obese individuals was released; it was by far the most exhaustive study of its kind, following these men and women for up to 20 years and meticulously recording their weights and diets. And, contrary to popular opinion, the study showed that the types of food you eat matter quite a bit — so yes, it matters where your calories come from. Dr. Dariush Mozaffarian of the Harvard School of Public Health and lead author of the study says, “What you eat makes quite a difference. Just counting calories won’t matter much unless you look at the kinds of calories you’re eating.”

“The body breaks down macronutrients — fats, carbs and protein — differently,” says Amy Shapiro MS, RD, CDN of Real Nutrition NYC. “Carbs get broken down quickly and turned into sugar in our systems, fat and protein less quickly. So, carbs spike our insulin and blood-sugar levels, causing us to store fat if they are not used as energy.” She continues, “Fat and protein are broken down more slowly, so they keep us feeling full longer on fewer calories and do not cause as many hormonal spikes.” It’s important to weigh all the attributes of your food — its caloric composition, nutritional composition, and fiber composition — against each other.

“One of the biggest misconceptions I encounter in my practice is the idea individuals have that if you dramatically reduce calorie count, then you’ll lose weight, says Marissa Lippert, MS, RD, dietitian and owner of a West Village restaurant, Nourish. She explains, “Most people will cut calories because they think it’s the best way to drop weight quickly. But, at bare minimum, most females should never go below 1,100 calories per day.” Your body needs calories just to work — to breathe, beat your heart, and regulate your body temp. In fact, an average 25-year-old woman uses approximately 1,300 calories just sitting around doing nothing. Add exercise, or even just walking to and from work, and you’ll need more calories.

When you go too low, calorically, you’re sending your body signals that a famine is near — probably not what you were going for. In response, your metabolism slows to a crawl and your body starts packing away fats to prepare for the metaphorical winter. So, if weight loss is your goal, then just blindly slashing the number of calories you consume each day isn’t going to do much.

It’s also essential to realize that just because calories are in food, doesn’t mean that your body will absorb them. You can think of your body’s digestion system like breaking open a delicious piggy bank (a food) to grab all the money (calories) inside. But, sometimes, no matter how hard you shake that bank, it doesn’t crack open and you can’t get out those last, few quarters. Something similar happens with calories in cooked versus uncooked foods.

When you cook a food, you’re basically breaking it down before you even put it in your body — cells split open, allowing your body to more easily access the stuff inside. When mice are given either cooked meat and sweet potatoes or raw meat and sweet potatoes, they gain more on the cooked stuff. So, when considering the number of calories in any food, it’s important to know that the number your body will actually absorb can vary.

And, what about the epic battle between processed foods and whole foods? If you needed any further proof that a "light" snack of crackers and cheese whiz isn’t a winning nutritional combination — and that processed foods should be avoided generally — researchers have discovered that our bodies digest processed and whole foods in entirely different ways. In fact, in an experiment where participants were given a 600-800 calorie snack of either whole-grain bread with a slice of cheddar cheese, or refined white bread and a “cheese product,” participants expended twice the number of calories breaking down all that hearty, natural food than they did the processed. For this particular snack, that meant the whole grain snackers actually received 10% fewer net calories than the other group (because they expended so many of those calories breaking everything down). Throw out your Wonder Bread, ladies and gents.

Keeping track of caloric intake is probably helpful — it gives us a rough idea of whether the amount of food we’re eating on any given day is reasonable. But, healthy nutrition has got to go way, way beyond just using your calculator watch to tally up two slices of bread. What we eat matters just as much as those pesky little calories. http://blogs.scientificamerican.com/guest-blog/2012/08/27/the-hidden-truths-about-calories/