Carbohydrates are macronutrients which the body uses to obtain energy and properly function. Carbohydrates, or carbs for short, are sugars, starches, and fibers found in vegetables, grains, fruit, and a variety of other foods.
Macronutrients are what make up the caloric content of a food. There are three types of macronutrients: carbohydrates, fat, and protein. Fat and protein are required in a person's diet because the body cannot produce them on its own. However, the optimal macro ratios for a healthy lifestyle are still a matter of debate.
Not all macronutrients supply energy in the same way. Here's a caloric breakdown for each type of macro:
- 1 gram of carbohydrates = 4 calories;
- 1 gram of fat = 9 calories;
- 1 gram of protein = 4 calories.
Carbohydrates are called this way because, chemically speaking, they are formed out of carbon, hydrogen, and oxygen. Two major components join to form carbohydrates. These are aldehydes (double-bonded carbon and oxygen atoms, plus a hydrogen atom) and ketones (double-bonded carbon and oxygen atoms, plus two additional carbon atoms).
Carbs are stored in the body in two forms: as glycogen in the liver (⅓) and in skeletal muscles (⅔). Your glycogen stores provide you with energy during physical activity and are replenished when you eat a meal rich in carbs. Once glycogen stores are full, extra carbs are stored as fat. Conversely, if you have insufficient carbohydrate intake or stores, the body will consume protein for fuel, which also means that you'll lose muscle -- which is not recommended.
According to The Academy for Nutrition and Dietetics, carbohydrates should account for 50% of daily caloric intake for the average adult, or around 250 grams of carbs per day. However, people with diabetes should not consume more than 200 grams of carbs per day.
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The types of carbs
Carbs can be either simple or complex.
Complex carbs are preferable to simple sugars because they don't lead to blood sugar spikes. Complex carbs are also richer in minerals, contain fiber, and make you feel fuller for longer.
The main difference between complex and simple carbs is in the way they are absorbed and digested. Simple carbs are digested and absorbed more quickly than complex carbs, which means they can provide bursts of energy faster. At the same time, simple carbs also cause sugar highs, while complex carbs provide energy over a longer time.
While simple carbs may be flashier, complex carbs get the job done better. What's more, due to their high glycemic index, simple carbs (or refined carbs, as they're also known) -- foods such as sugar-sweetened beverages, fruit juices, pastries, white bread, white pasta, white rice, and others -- are associated with various health problems like obesity, heart disease, and type 2 diabetes.
Simple carbs also tend to cause major spikes in blood sugar levels, which later lead to a crash that can trigger hunger, leaving a person craving more high-carb foods.
So, not all carbs are created equal. Refined carbs can lead to obesity and metabolic diseases, while unrefined carbs (or complex carbs) are healthy.
Sources of complex carbs:
- Legumes (i.e. peas, lentils, chickpeas, beans);
- Cereals and grains;
- (Sweet) potatoes;
- Whole-grain products;
- Brown rice;
Examples of simple sugars:
- Products containing refined or bleached flour;
- Sweetened soft drinks and fruit juices.
Carbs are differentiated by chain length into the following groups:
- Monosaccharides: glucose (corn sugar), fructose (fruit sugar), galactose (milk sugar);
- Disaccharides: sucrose (table sugar), lactose (dairy);
- Oligosaccharides: melitose;
- Polysaccharides (aka complex carbohydrates): amylopectin (plant starch), glycogen (animal starch), inulin.
From a dietary standpoint, nutritionists talk about carbs in term of:
- Sugars: Sweet, short-chain carbohydrates found in foods.
- Starches: Long chains of glucose molecules which eventually get broken down into glucose in the digestive system.
- Fiber: Humans cannot digest fiber, although the bacteria in the digestive system can make use of some of them. These bacteria can use the fiber to produce fatty acids that some of our cells can use as energy.
Carbohydrates and your body
Carbohydrates are your body's main source of fuel. In fact, your body needs them in order to function well. During digestion, carbs such as sugars and starches are broken down into simple sugars, which are subsequently absorbed into the bloodstream (blood glucose). The glucose eventually makes its way into cells, with the help of insulin, where it used for energy. Extra sugars are stored in the liver, muscles, and other cells. 'Extra-extra' sugars are stored as fat.
While fibers aren't directly digested in the human gut, including them in your diet helps control weight by making you feel full on fewer calories. Fiber can also offer protection against obesity and type 2 diabetes.
If blood glucose levels rise too rapidly and too often, cells can eventually become faulty and not respond properly to insulin's instructions. This generally happens when a person's diet consists of carbs high in glycemic index, which enter the bloodstream quickly as glucose. Over time, the cells need increasing amounts of insulin to react, causing insulin resistance.
After producing high levels of insulin for many years, the beta cells in the pancreas can wear out. Insulin production drops and eventually can stop altogether. The person now has diabetes.
Do carbs make you fat?
People who are overweight or obese can lose weight by following a low-carb diet. A seemingly logical conclusion is that these people gained weight because of carbs -- but this is not true. Humans have been consuming carbs long before the spread of the obesity epidemic that is rampant today in the United States (and the type 2 diabetes that naturally followed soon after). Think of Asian populations that have subsisted on high-carb diets (i.e. rice) for millennia while maintaining relatively good health with low of incidence of obesity.
In 1962, 46 percent of adults in the U.S. were considered overweight or obese. By 2010, that figure had jumped to 75 percent. The culprit? Obesity is a complex condition with multiple causes, but among its many suspects, added sugar is at the top of the list. Scientific literature is filled with evidence linking sugar to a variety of chronic diseases, including obesity, cardiovascular disease, diabetes and non-alcoholic fatty liver disease (NAFLD) as well as cognitive decline and even some cancers.
The average American eats a whopping 20 teaspoons of sugar every day, according to U.S. government figures. That’s well above the American Heart Association’s recommendation of 6 teaspoons per day for women and 9 per day for men.
“I don’t think we have enough evidence yet to suggest that sugar is the reason for the obesity epidemic,” said Johns Hopkins cardiologist Chiadi E. Ndumel. “But there is enough evidence to say that elevated sugar consumption is an important contributor to weight gain.”
So, it's not carbs per se that make you fat, but rather refined carbs and processed foods.
There's also something that ought to be said for low-carb diets. Replacing much of a person's carb intake with healthy sources of protein and fat has been shown to result in weight loss. The low-carb diet was most beneficial for lowering triglycerides, the main fat-carrying particle in the bloodstream, and also delivered the biggest boost in protective HDL cholesterol.
But more recent studies show that while low-carb diets offer health benefits in the short-term, they can cause problems over the long-run. A study of 15,428 American adults found that, over a 25-year period, people who had a moderate carbohydrate intake (50-55% of daily calories) had an average life expectancy of 83 years — slightly longer than those with low carb intake (40%), who lived only 79 years on average. Participants with a high carb intake (more than 70% of daily calories) had an average life expectancy of 82 years, slightly lower than the moderate carbs intake group. Another study published this year found that people on a low-carb diet had a greater risk of premature death, particularly due to coronary heart disease, stroke, and cancer.
Bearing all of this in mind, it's perhaps better to focus on including healthy carbs in your diet rather than cutting back on the nutrient. It's also helpful to remember that there is no one-size-fits-all solution in nutrition. An optimal carbs intake will depend a lot from person to person and be based on numerous factors, such as age, gender, metabolic health, physical activity, food culture, and personal preference. For instance, a person with type 2 diabetes will have to include fewer carbohydrates in their diet. On the other hand, if you're a healthy person, there's no reason to avoid complex carbohydrates.
Here are some tips you can try in order to cut back on refined carbs:
- Avoid sodas and other sugar-sweetened beverages;
- Reach for fruits instead of candy, cookies or other sweet treats;
- Read ingredient labels carefully. You'll find sugar hiding in unexpected places, such as spaghetti sauce and sandwich bread.
- Added sugars come by many names. When reading labels, keep an eye out for terms like corn sweetener, corn syrup, dextrose, fructose, glucose, high-fructose corn syrup, honey, lactose, malt syrup, maltose, molasses, raw sugar, and sucrose.
Generally, carbs which can be found in their natural, fiber-rich form are healthy and do not cause weight gain, unlike processed and refined carbs. There are 'good' carbs and there are 'bad' carbs. A well-balanced diet that includes complex carbs, along with getting proper sleep and physical activity is more likely to keep a person in good health than focusing on eliminating a particular nutrient.