Emus do not process food; neither, to any real extent, do any of the apes. Yet every human culture in the world has technology for modifying its food. We grind, we heat, we ferment. When humans learned to cook food—particularly, meat—they would have dramatically increased the number of calories they extracted from that food. Wrangham proposes that getting more energy from food allowed humans to develop and nourish exceptionally large brains relative to body size.
But no one had precisely investigated, in a controlled experiment, how processing food changes the energy it provides—until now. Rachel N. Carmody, a former graduate student in Wrangham's lab, and her collaborators fed adult male mice either sweet potatoes or lean beef. She served these foods raw and whole, raw and pounded, cooked and whole, or cooked and pounded and allowed the mice to eat as much as they wanted for four days.
Mice lost around four grams of weight on raw sweet potatoes but gained weight on cooked potatoes, pounded and whole. Similarly, the mice retained one gram more of body mass when consuming cooked meat rather than raw meat. This reaction makes biological sense. Heat hastens the unraveling, and thus the digestibility, of proteins, as well as killing bacteria, presumably reducing the energy the immune system must expend to battle any pathogens. Carmody's findings also apply to industrial processing.
Even if two people eat the same sweet potato or piece of meat cooked the same way, they will not get the same number of calories out of it. Carmody and her colleagues studied inbred mice with highly similar genetics. Yet the mice still varied in terms of how much they grew or shrank on a given diet. People differ in nearly all traits, including inconspicuous features, such as the size of the gut.
Measuring people's colons has not been popular for years, but when it was the craze among European scientists in the early s, studies discovered that certain Russian populations had large intestines that were about 57 centimeters longer on average than those of certain Polish populations.
Because the final stages of nutrient absorption occur in the large intestine, a Russian eating the same amount of food as a Pole is likely to get more calories from it. People also vary in the particular enzymes they produce.
By some measures, most adults do not produce the enzyme lactase, which is necessary to break down lactose sugars in milk. As a result, one man's high-calorie latte is another's low-calorie case of the runs. People differ immensely as well in what scientists have come to regard as an extra organ of the human body—the community of bacteria living in the intestines.
In humans, two phyla of bacteria, Bacteroidetes and Firmicutes, dominate the gut. Researchers have found that obese people have more Firmicutes in their intestines and have proposed that some people are obese, in part, because the extra bacteria make them more efficient at metabolizing food: so instead of being lost as waste, more nutrients make their way into the circulation and, if they go unused, get stored as fat.
Other microbes turn up only in specific peoples. Some Japanese individuals, for example, have a microbe in their intestines that is particularly good at breaking down seaweed. It turns out this intestinal bacterium stole the seaweed-digesting genes from a marine bacterium that lingered on raw seaweed salads.
Because many modern diets contain so many easily digestible processed foods, they may be reducing the populations of gut microbes that evolved to digest the more fibrous matter our own enzymes cannot.
If we continue to make our gut a less friendly environment for such bacteria, we may get fewer calories from tough foods such as celery. Few people have attempted to improve calorie counts on food labels based on our current understanding of human digestion. We could tweak the Atwater system to account for the special digestive challenges posed by nuts.
We could even do so nut by nut or, more generally, food by food. Such changes which have unsurprisingly been supported by the Almond Board of California, an advocacy group would, however, require scientists to study each and every food the same way that Novotny and her colleagues investigated almonds, one bag of feces and jar of urine at a time.
Judging by the fda's regulations, the agency would be unlikely to prevent food sellers from adjusting calorie counts based on such new studies. The bigger challenge is modifying labels based on how items are processed; no one seems to have launched any efforts to make this larger change.
Even if we entirely revamped calorie counts, however, they would never be precisely accurate because the amount of calories we extract from food depends on such a complex interaction between food and the human body and its many microbes. In the end, we all want to know how to make the smartest choices at the supermarket.
Merely counting calories based on food labels is an overly simplistic approach to eating a healthy diet—one that does not necessarily improve our health, even if it helps us lose weight. Instead we should think more carefully about the energy we get from our food in the context of human biology.
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Underweight children aged 2 to 5 Underweight children aged 6 to Advice for parents of healthy-weight children. The amount of energy in an item of food or drink is measured in calories. For an average woman, that figure is around 2,kcal 8,kJ a day.
Check if you're a healthy weight by using our body mass index BMI calculator Calories and energy balance Our bodies need energy to keep us alive and our organs functioning normally. For example, the more physical activity we do, the more energy we use. Checking calories in food Knowing the calorie content of food and drink can help ensure you're not consuming too much. Many labels will also state the number of calories in 1 portion of the food.
Calorie counters There's a wide range of online calorie counters for computers and mobile phones. Calories should be given per portion or per meal. Fruit juice has nutrients but is calorie dense, providing energy in the form of sugar.
Beer, made from fermented grains, contains calories from both alcohol and carbs. Non-alcoholic beverages can be non-caloric, like water and tea, or high calorie like cola. Soft drinks like soda contain sugar or other sweeteners and are often empty calories.
The standard glass of table wine has about calories, but sweet varieties have more. Most calories in whole grains and cereal products come from complex carbohydrates. Oatmeal and other cereals offer mostly carbohydrate calories, including dietary fiber. Since pasta and noodles are made almost entirely of flour, the calories are mostly carbs.
Calories in dishes and meals are calculated by totaling the nutrition of all ingredients. Soups are often low in calories, but check the label since any foods can be included. Beans and other legumes are nutritional foods with calories from carbs, fat, and protein. Nuts and seeds are high in fat and therefore calorie dense, but they are very nutritious. Calories from oils are pure fat, but certain varieties like avocado are heart-healthy. Vegetable oils have the same calories as animal fat but are suitable for all diets.
Baking ingredients can contain a lot of calories, like sugar, or very little, like spices. Fish and seafood are often low in fat and therefore calories, providing mostly protein. Herbs and spices often add negligible calories to a meal but offer high nutritional value. Breads like sprouted wheat are very nutritious, whereas pastries can be empty calories. Sauces and dressings seem like a small addition but can add significant calories.
Spreads are calorie dense, whether they are mostly fat like tapenade or sugar like honey. Counting calories has never been faster and easier. Get an overview of your nutrition by downloading this free calorie counter app. While quality of food is important for a healthy diet, quantity is also a major factor of good nutrition. Those extra calories, after all, are converted to excess body fat. One hundred calories of peanut butter, for example, is only a spoonful or two. But one hundred calories of vegetables can equal several cups!
Calories are a unit of measurement to show how much energy you will get from a serving of food. Before they get stored as fat, the calories in food are converted into fuel for everything from organ and brain functions to walking around and even just sitting upright.
The number of calories your body needs for minimal functions — that is, simply lying in bed all day — is called basal metabolic rate BMR. Then, how much you move and how vigorously determines if you have room in your healthy diet for more calories. Very active individuals should use the nutrition database to locate foods with a lot of energy, as indicated in the calorie chart by a high number per serving.
Those whose lifestyles involve minimal activity, such as commuting to an office job by car, should look at nutrition facts to plan meals that have larger portions with fewer calories; same goes for anyone following a weight loss diet.
Healthy eating habits must revolve around a balanced diet, and that means getting a mix of complex carbohydrates, good fats, and lean proteins. In general, healthy foods are not processed and contain a lot of nutrients like vitamins, minerals and antioxidants.
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