Diet ResearchMacro & MicronutrientsNutritionWeight

Do Carbs Make You Fat?

Carbohydrates do not make us fat or sick.

Carbohydrates do not make you fat or sick, eating the wrong sorts of foods for a human does. As Dr. McDougall emphatically points out,

“All large populations of trim, healthy people, throughout human history, have obtained the bulk of their calories from starch.”

The idea that carbohydrates make us fat or sick is a myth that is not founded in science. Rather, a parade of diet gurus and trends have made carbohydrates the enemy. As with many false myths, this one may have begun with a kernel of truth. The kernel of truth here is that processed sugar and ultra-processed carbohydrates are not health foods and can contribute to a host of health problems—just like all ultra-processed foods. But, as the authors of The Whole Foods Diet state,

“As much as refined sugar may deserve crucifixion, it can’t die for all our dietary sins!” 

What Exactly are Carbs?

As basic as this question is in the realm of nutrition, it’s amazing how little many people know about what a carbohydrate really is. Carbohydrates are one of three essential macronutrients that provide the energy we humans, and other living creatures, need to survive. Fat and protein are the other two. Fiber and water are two other macronutrients, nutrients we require in relatively large amounts, but these don’t provide energy. Carbohydrates, “carbs,” are the human body’s preferred source of fuel. Carbs are easiest for the body to break down and are, quite conveniently, most easy for us to obtain when you think about the bigger picture. Fresh fruits, vegetables, starchy roots, and grains are all natural sources of carbohydrates. However, they aren’t purely “carbs.” These natural whole plant foods contain the full spectrum of macronutrients and micronutrients. They contain a symphony of fat, protein, vitamins, minerals, phytonutrients, fiber, water, and carbs. Many people label breads and cookies as “carbs.” While it’s true that bread and cookies both contain carbohydrates, bread also contains protein, some fat, fiber, and many other micronutrients. Cookies are typically composed of equal parts fat and carbohydrates, so it is just as fair to call cookies or cakes a “fat” food as it would be to call them a “carb” food. The reality is that, unless you are dealing with purely processed sugar or oil, most all foods are composed of a combination of macro- and micronutrients. All of these nutrients are required in some degree for a healthy body and none of these should be picked out to be demonized and blamed for all of our health woes.

The Carbohydrate-Insulin-Obesity Hypothesis

Just where did all this carb-bashing come from? Fad diet book authors and gurus have made many millions on the attractive theory that eating a diet high in fatty animal foods is the ticket to weight loss and health. Their premise is known as the Carbohydrate-Insulin-Obesity Hypothesis. These proponents of low-carb diets suggest that carbohydrates drive fat storage and obesity because carbs raise insulin levels. According to their theory, insulin blocks the release of fat and promote fat storage in the body, but nutrition science begs to differ. Thankfully, we don’t have to wait, wonder, or be guinea pigs for the next low-carb craze. The science is in, and there is really no debate about it. Study after study has found no association between carbohydrate consumption and fat storage.

Study Shows Carbohydrate Intake Reduces Risk for Overweight and Obesity

One way to look at the impact of carb-consumption on weight is with cross-sectional analysis comparing reported diets of a large group of people with their BMI and obesity status. One such study looked at the 24-hour dietary recall of 4,451 Canadians and analyzed the data against the participants BMI and weight status (= normal, overweight, or obese). They found that people who had the lowest intake of carbohydrates had the greatest rates of overweight and obesity. Those who ate the highest carbohydrate diets were at lowest risk for being overweight (Merchant, 2009).

32 Studies Confirm That Eating More Carbs Is Good for Weight Loss

To see if which macronutrient you eat more of matters for weight loss or weight gain, researchers can put subjects on controlled diets and monitor their weight and other health indicators. These studies put different groups of people on diets that are exactly the same in terms of calorie-content (“isocaloric”), but either dominated by carbs or dominated by fat. Then researchers look for different outcomes between the two diets. There have been numerous such studies over the last few decades. A 2017 meta-analysis published in the journal Gastroenterology looked at the results of 32 controlled feeding studies where participants where fed the same number of calories, but with different macronutrient ratios. The results of these studies revealed that both fat loss and energy expenditure were greater with lower fat/higher carbohydrate diets (Hall, 2017).

Study Shows Eating Carbs Doesn’t Make You Fat

It’s good to know that a carbohydrate-rich diet has the edge when it comes to weight loss, but are you at risk of gaining more weight if you eat extra carbs compared to fat? This type of study flips our question on its head. Instead of restricting the diets of subjects and seeing which group loses the most weight, another type of study purposely overfeeds people on either a carb-rich diet or a fat-rich diet and then looks for a difference in outcome. Do carbs make you fat while fat keeps you skinny? Is there a difference in consuming extra fat versus extra carbs? One study put this question to the test with a group of 16 men who were fed 150% of their caloric requirements with a high fat diet and then with a high carb diet. The result? – Both overfeeding diets caused nearly identical increases in body weight and fat mass, but those on the extra fat seemed to fare worse. Those extra carb calories were stored at a rate of 75-85% while the remainder of the excess was consumed by increased energy expenditure. Those consuming extra fat calories, on the other hand, stored 90-95% of those calories. The researchers concluded,

“Excess dietary fat leads to greater fat accumulation than does excess dietary carbohydrate, and the difference was greatest early in the overfeeding period.”

(Horton, 1995).

Another similar study that overfed 20 lean men found no difference between over-eating carbs or over-eating fat after 21 days. Whether you eat a 1000 calories of carbs more than you expend or 1000 calories more of fat than you expend, this studies suggest you are going to gain exactly the same amount of weight (Lammert, 2000).

Not All Carbs Are Created Equal

We are used to hearing about “bad fat” and “good fat” and “bad carbs” and “good carbs.” While these categories may be a bit simplistic, there is an important distinction to be aware of. Whole foods are, without a doubt, more nutritious and wellness-promoting foods when compared to processed foods. There’s just no comparing apples to soda when it comes to carbohydrates. Just because soda is loaded with carbs, does not make it a healthy choice. Here’s why. Whole plant foods are rich in healthy carbohydrates, which are our body’s preferred source of energy. These carbohydrates come packed with a symphony of other nutrients—protein, fat, fiber, water, vitamins, minerals, and phytonutrients—that together work to give us energy, maintain a healthy body, and prevent disease. There is a big difference between eating lollipops and sweet potatoes—both foods are rich in carbohydrates—or eating cherries versus drinking cherry cola. Sweet potatoes and cherries are whole plant foods which benefits our health in numerous ways. Lollipops and soda are made of processed sugar and artificial ingredients which do little to aid our health. These are empty calorie foods, they neither nourish our bodies or satiate our appetites. Too many processed foods, like lollipops, or too many high-fat animal foods can lead us down the path of weight gain and disease.

Whole Plant Carbs Are The Ticket to Health

Carbohydrates are essential macronutrients that are naturally occurring in the healthiest foods. Eating carbs alone doesn’t make you fat and won’t get in the way of losing weight. In fact, studies show that a diet rich is carbohydrates is both advantageous to losing weight as well as maintaining a healthy weight. Not all carbohydrates are the same, but if you choose whole plant foods you will be getting a healthy dose of carbohydrates along with all the other good stuff in nature’s perfect cocktail of nutrients that promote wellness and prevent today’s most common chronic diseases.

1. Hall, Kevin D. "Obesity Energetics: Body Weight Regulation and the Effects of Diet Composition." Gastroenterology VOLUME 152, ISSUE 7, P1718-1727.E3, MAY 01, 2017.
2. Horton, T J et al. “Fat and carbohydrate overfeeding in humans: different effects on energy storage.” The American journal of clinical nutrition vol. 62,1 (1995): 19-29. doi:10.1093/ajcn/62.1.19
3. Lammert, O et al. “Effects of isoenergetic overfeeding of either carbohydrate or fat in young men.” The British journal of nutritionvol. 84,2 (2000): 233-45.
4. Merchant, Anwar T et al. “Carbohydrate intake and overweight and obesity among healthy adults.” Journal of the American Dietetic Association vol. 109,7 (2009): 1165-72. doi:10.1016/j.jada.2009.04.002

Reya Steele Andrews

Reya (Steele) Andrews is a holistic health writer, educator, and publisher at Healing With Plants. Reya is a certified Holistic Nutritionist (AFPA), is certified in Plant-based Nutrition, and teaches nutrition science and healthy food preparation. Find her book, The Frugivore Diet, on Amazon.

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