In recent years, there has been a longstanding stigma attached to carbohydrates being considered the nemesis of having an ideal body composition. People usually start eliminating foods such as bread, rice, pasta, and potatoes from their diet whenever they plan on losing weight. But do carbs make you gain weight, or is it unfair to place all the blame on carbohydrates for making one overweight?
The true answer, based on years of nutritional science, is that carbohydrates are not really what makes one fat. Whether or not eating carbs makes you gain weight depends on the type of carbohydrates consumed, total calorie intake, activity levels, and how the body reacts to different foods. Let us look into the facts.
What Are Carbohydrates, Really?
There are three major groups of macronutrients, and carbohydrates are one of them, along with proteins and fats. Carbohydrates are the most effective source of energy for the human body because they are converted into glucose. However, not all types of carbohydrates function similarly in the body.
Simple Carbohydrates
These are fast-absorbed sugar forms that are found in sweets, beverages, white breads, and bakery items. These give a quick rise in the glucose level of the blood, but that is soon followed by a quick fall.
Complex Carbohydrates
These kinds of carbs are found in whole grain foods, beans, vegetables, and fruits. Because of the fiber that they contain, these carbs take longer to digest compared to simple carbs.
This distinction is a major reason why blanket statements like "carbs cause weight gain" oversimplify what is actually a nuanced relationship between food quality, portion size, and metabolism, and it's a big part of the answer to whether carbohydrates make you gain weight in the first place.
The Insulin Theory: Where the "Carbs Make You Fat" Idea Comes From
A substantial portion of the general perception of carbohydrates being fattening can be attributed to the carbohydrate-insulin hypothesis of obesity, formulated mostly by Harvard professor David S. Ludwig along with Cara Ebbeling, his fellow scientist. The carbohydrate-insulin hypothesis suggests that foods rich in carbohydrates with a high glycemic index initiate an increase in insulin levels, the hormone responsible for the transportation of glucose into the cells (Ludwig & Ebbeling, 2018).¹ Further elaborating on their theory, researchers stated that an increase in insulin production makes the organism convert more calories into fat and use less fuel for other organs, thus increasing appetite and reducing the expenditure of energy (Ludwig et al., 2021).² In this way, overeating is seen as a consequence rather than a cause of the fat storage process.²
The Counterargument: The Energy Balance Model
Not everyone who does research in this area is convinced by the hormonal theory. Kevin D. Hall, who was previously a scientist at the National Institutes of Health, along with his co-authors, Stephan Guyenet and Rudolph Leibel, wrote a response in which they argue that the carbohydrate-insulin model is incompatible with the neuroendocrine data about obesity (Hall, Guyenet, & Leibel, 2018).³ In subsequent metabolic ward studies conducted by Kevin D. Hall in which he compared a low-fat diet with plenty of vegetables with a low-carbohydrate ketogenic diet with plenty of animal foods, participants eating the low-fat diet consumed several hundred fewer calories daily than those eating the ketogenic diet (Hall et al., 2021).⁴
Hall and a whole bunch of collaborators, including obesity scientists who have never collaborated with him before, described an energy balance theory where body weight depends on calories eaten and burned off and where insulin has only an accessory function (secondary) while not being a key cause (Hall et al., 2022).⁵ In reaction to the claim that Hall’s own experiment in 2021 supports the insulin theory, Hall and his team came up with their rebuttal on statistical grounds (Sciarrillo et al., 2024).⁶
Where the Science Currently Stands
It is still an ongoing discussion among the scientific community, where people from either side publish their counterarguments and evidence in journals such as JAMA Internal Medicine and The American Journal of Clinical Nutrition.¹²³⁵ Some reviews point out that even though the mechanisms and some short-term studies partially prove the points in the carbohydrate-insulin hypothesis, the majority of longer-term studies prove the energy balance hypothesis right. Most scientists from both camps, however, share one common idea: high-glycemic carbohydrates are associated more with overeating and obesity than whole carbohydrate sources.
So, Do Carbs Make You Gain Weight?
The most accurate answer to whether carbs make you gain weight is: they do only when they contribute to a calorie surplus, same as excess intake of protein and fats.⁵ The reason why one gains weight is the consumption of more calories than the body expends.
However, there are specific carbohydrate tendencies that make it easy to overeat:
Rapidly digested carbohydrates cause rapid spikes in blood glucose levels followed by crashes, resulting in increased appetite.
Carbohydrates lacking dietary fiber are generally not satiating; therefore, they enable consumption of large quantities without getting full.
Processed and highly palatable carbohydrates (like snacks and soda) are designed to facilitate overconsumption.
Why Low-Carb Diets Often Work (But Not for the Reason You Think)
It is well observed that many individuals have succeeded in losing weight through low-carbohydrate diets; this appears to validate the concept that carbohydrates are responsible for obesity. The success achieved by such dieters is mainly attributed to several indirect causes instead of high levels of carbohydrates causing obesity.⁴ ⁵
Calorie reduction: The elimination of one food group automatically means there is less food available to snack on.
Increased protein and fat intake: Both protein and fats are more satiating and therefore reduce caloric intake indirectly.
Exclusion of processed foods: Processed foods are usually high in both carbs and calories, and eliminating them means calorie reduction.
Weight loss due to water loss: When carbs are eliminated, the stored glycogen gets depleted. One gram of glycogen binds four to five grams of water.
How to Eat Carbs Without Gaining Weight
There is no need for you to cut out all carbohydrates to lose or maintain weight. What you need to concentrate on is carbohydrate quality and portion size.
Opt for Whole Foods
Select oats, quinoa, brown rice, sweet potatoes, legumes, and fruits over white bread, cereal, and pastry.
Combine Your Carbohydrates with Protein and Fiber
When you eat carbohydrates with protein or fats, you digest them more slowly, avoid blood sugar fluctuations, and feel fuller.
Watch Portion Sizes
Even healthy carbs provide energy. Knowing your portion size, especially for high-calorie foods such as nuts, granola, and dried fruit, will help you maintain a healthy weight.
Schedule Your Carbohydrates to Fit Around Exercise
Highly active people can afford to eat more carbs because their glycogen stores are constantly being used and replenished through workouts.
Frequently Asked Questions
Do carbs really make you gain weight?
But not by themselves. It is only because carbohydrates make you eat more calories than you burn that they cause weight gain.⁵ What matters much more than just eating carbs is what kind of carbohydrates you are eating and how much.
Which carbs are most likely to cause weight gain?
Refined, fiber-poor carbohydrates such as white bread, sugary cereals, baked goods, and soft drinks have been shown to be more associated with overconsumption and obesity than their whole counterparts like oats, beans, quinoa, and fruits due to their quick digestion and poor satiating effect.
Is the carbohydrate-insulin model of obesity proven?
No, it remains an open hypothesis as opposed to an undisputed fact. This theory is supported by researchers such as David Ludwig,¹² while, on the other hand, Kevin Hall and Rudolph Leibel believe that controlled feeding trials confirm the energy balance hypothesis.³⁴⁵⁶
Why do I lose weight quickly on a low-carb diet?
Most of the initial loss in weight in low-carbohydrate diets occurs because of depletion of glycogen, which leads to the release of associated water, along with the inherent reduction in the total calorie consumption by eliminating one complete group of foods.
Can I eat carbs and still lose weight?
Absolutely. Selecting whole, unrefined carbohydrates, combining them with protein or fiber, and being mindful of portion control enables most individuals to incorporate carbohydrates into their diet while remaining within a calorie deficit to lose weight.
Are some people more sensitive to carbs than others?
Metabolic reactions to carbohydrates are not consistent for everyone, as they are influenced by different variables such as insulin sensitivity, exercise, and gut condition. This explains why some people are able to lose weight more effectively with higher carbohydrate intakes compared to others.
Key Points
Carbohydrates need not necessarily be seen as the evil perpetrator when it comes to gaining weight. There is an ongoing scientific discussion between the carbohydrate-insulin hypothesis put forward by David Ludwig ¹² on one side and the energy balance hypothesis supported by nutritionists like Kevin Hall and Rudolph Leibel ³⁴⁵⁶ on the other side. However, what is evident is the importance of considering the type of carbohydrates consumed and their quantity, along with the dietary intake of the individual, rather than just the avoidance of one macronutrient class.
References
1. Ludwig DS, Ebbeling CB. The Carbohydrate-Insulin Model of Obesity: Beyond "Calories In, Calories Out." JAMA Intern Med. 2018;178(8):1098–1103. doi:10.1001/jamainternmed.2018.2933. PMID: 29971406
2. Ludwig DS, Aronne LJ, Astrup A, et al. The carbohydrate-insulin model: a physiological perspective on the obesity pandemic. Am J Clin Nutr. 2021;114(6):1873–1885. doi:10.1093/ajcn/nqab270. PMID: 34515299
3. Hall KD, Guyenet SJ, Leibel RL. The Carbohydrate-Insulin Model of Obesity Is Difficult to Reconcile With Current Evidence. JAMA Intern Med. 2018;178(8):1103–1105. doi:10.1001/jamainternmed.2018.2920
4. Hall KD, Guo J, Courville AB, et al. Effect of a plant-based, low-fat diet versus an animal-based, ketogenic diet on ad libitum energy intake. Nat Med. 2021;27(2):344–353. doi:10.1038/s41591-020-01209-1. PMID: 33479499
5. Hall KD, Farooqi IS, Friedman JM, et al. The energy balance model of obesity: beyond calories in, calories out. Am J Clin Nutr. 2022;115(5):1243–1254. doi:10.1093/ajcn/nqac031. PMID: 35134825
6. Sciarrillo CM, Guo J, Hengist A, Darcey VL, Hall KD. Flawed reanalysis fails to support the carbohydrate-insulin model of obesity. J Nutr. 2024;154(3):1058–1060. doi:10.1016/j.tjnut.2024.01.024. PMID: 38286396
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