Are Carbs Really Addictive?

The debate on whether carbs are good or bad and their role in optimal health have dominated discussions of the human diet for quite a long time.

The recommendations on carbs have changed consistently year after year due to the mainstream diet fads and popularity of certain so called beneficial diets.

Researchers are continually discovering new information about how your body digests and responds to carbs.

Therefore, you may still be extremely confused and wondering how to include carbs in a healthy diet, or what makes some carbs so hard to turn away from at times.

I’ll examine the current research on whether carbs are addictive, and what that means for their role in your diet.

What exactly are carbs?  

Carbs, or carbohydrates, are molecules that have carbon, hydrogen and oxygen atoms.

In nutrition, "carbs" refers to one of the three macronutrients. The other two are protein and fat.

Dietary carbohydrates can be split into three main categories:

• Sugars: Sweet, short-chain carbohydrates found in foods. Examples are glucose, fructose, galactose and sucrose.
• 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.

The main purpose of carbohydrates in the diet is to provide energy. Most carbs get broken down or transformed into glucose, which can be used as energy. Carbs can also be turned into fat (stored energy) for later use.

Fiber is an exception. It does not provide energy directly, but it does feed the friendly bacteria in the digestive system. These bacteria can use the fiber to produce fatty acids that some of our cells can use as energy.

Sugar alcohols are also classified as carbohydrates. They taste sweet, but usually don't provide many calories.

Are carbs really addictive?

Sometimes you can just feel that tasty, highly palatable carb calling your name!  It’s extremely enticing and very hard to resist! You think about it constantly and go back and forth in your mind pondering whether you should just have a bite or two. Have you ever noticed that it can be quite challenging to defy junk food at times, especially carbs that are high in refined sugar, salt, and fat.

So what is the deal? Numerous people have contemplated the idea of this being willpower, behavioral or psychological traits, or even brain chemistry.

There are individuals who have gone as far as to question whether carbs could be addictive in the same way that other substances (i.e. alcohol) or behaviors can be [1]. 

With the increase in the worldwide prevalence of obesity over the past few decades [2] the concept of “food addiction” has recently become popular both among researchers and the general public as a possible way to understand the impact of psychological factors on weight gain.

This concept forms a contributory framework that is centered between chemical or “substance based” and behavioral addictions.

It’s argued that the rise in prevalence rates of obesity in many countries cannot be attributed to genetic factors alone; instead, environmental changes, which interact with our biological make-up, appear to underlie the obesity pandemic.

A large proportion of different populations overeat to an extent that threatens physical and mental well-being, and psychiatric disorders are associated with obesity. Experts argue that “Food addiction” offers a superficially attractive explanation, and potentially an excuse, for this unhealthy behavior at an individual level. 

The modern “obesogenic” environment is characterized by the universal availability of palatable, energy-dense and inexpensive foods, reflecting ongoing efforts of the globalized food industry to increase production and boost sales.

“Food addiction” places blame on the food industry for the production of “addictive foods” and by so doing indicates that obesity prevention strategies should seek to curtail the influence of this industry on eating behavior [1].

Another recent prominent study investigated the validity of the analogy between addictive drugs, like cocaine, and hyperpalatable foods, notably those high in added sugar (i.e., sucrose). They argue that available evidence in humans shows that sugar and sweetness can induce reward and craving that are comparable in magnitude to those induced by addictive drugs [3]. 

Overall, a review of the research in this area has revealed that sugar and sweet reward can not only substitute to addictive drugs, like cocaine, but can even be more rewarding and attractive. At the neurobiological level, the neural substrates of sugar and sweet reward appear to be more robust than those of cocaine (i.e., more resistant to functional failures), possibly reflecting past selective evolutionary pressures for seeking and taking foods high in sugar and calories. This may very well explain why many people can have difficultly to control the consumption of foods high in sugar when continuously exposed to them [3].

A recent study examined the effects of the glycemic index on brain activity in the late postprandial (i.e., after eating) period after a typical between-meal interval [4].

GI stands for glycemic index, which is a measure of how the carbs in a meal affect blood sugar levels. A food with a high GI increases blood sugar levels more dramatically than a food with a low GI.

This study showed that the consumption of a high- compared with a low-glycemic index meal increased the activity in brain regions related to food intake, reward, and craving in the late postprandial period, which was coincident with lower blood glucose and greater hunger [4].

The figure below shows that cerebral blood flow was greater 4 hours after the high- than low- glycemic index meal in the right nucleus accumbens.   

These findings, together with longer feeding studies of weight-loss maintenance [5], suggest that a reduced consumption of high-glycemic index carbohydrates (specifically, highly processed grain products, potatoes, and concentrated sugar) may ameliorate overeating and facilitate maintenance of a healthy weight in overweight and obese individuals.

Fig: Regions with significantly different cerebral blood flow 4 h after test meals (P ≤ 0.002). The color scale represents the value of the t statistic for the comparison between meals (n = 11) by using general linear model analyses as described in Subjects and Methods. For all areas depicted, the blood flow was greater after the high- than after the low-GI meal. GI, glycemic index [4].

The supporting evidence that carbs are addictive

Some scientists have suggested that refined carbs in the form of fructose have addictive properties that closely resemble those of alcohol. As a reminder; fructose is a simple sugar found in fruits, vegetables, and honey.

Some scientists have found that, like alcohol, fructose promotes insulin resistance, abnormal fat levels in your blood, and liver inflammation. Plus, it stimulates your brain’s pathway to the sense of pleasant sensations [6].

This pathway is referred to as the hedonic (i.e. pleasant sensation) pathway and is known to trigger appetite and influence food intake through a system of pleasure and reward rather than being based on true physical hunger or actual energy needs.

It’s clear that insulin resistance, inflammation, and abnormal fat levels increase your risk of chronic disease, but repeated stimulation of this hedonic pathway may reset the level of fat mass your body wants to preserve, contributing to increased body weight [7].

It’s also argued that high-GI (glycemic index) carbs that promote rapid changes to insulin and blood sugar levels also appear to affect dopamine levels.  The glycemic index is a number from 0 to 100 assigned to a food, with pure glucose arbitrarily given the value of 100, which represents the relative rise in the blood glucose level two hours after consuming that food. Dopamine is a neurotransmitter in your brain that sends messages between cells and influences the way you feel pleasure, reward, and even motivation [8].

After reviewing the pertinent literature; some scientists argue that food addiction is a plausible contributing factor to the heterogeneous condition of obesity. They stated that at least a subset of vulnerable individuals, high-glycemic-index carbohydrates trigger addiction-like neurochemical and behavioral responses [8].

In support of this line of evidence; some research in rats shows that granting periodic access to sugar and chow food mix may produce behavior that closely mirrors the dependency often seen with drug abuse [9]. An additional study using a similar model allowed rats periodic access to a 10% sugar solution and a chow food mix followed by a period of fasting. The rats displayed anxiety-like behaviors and a reduction in dopamine during and after the fast [10].

I think it is important to recognize that most of the experimental research conducted thus far on carbs and addiction has taken place in animals. Therefore, additional and more rigorous human studies are needed.

Supporting evidence that carbs are not addictive

On the other hand, some researchers are not convinced that carbs are truly addictive.

The premise for their argument is that there is not enough data on human studies and they claim that most of the research in animals suggests addiction-like behaviors from sugar rather than from the neurochemical effect of carbs in general [11].

These scientists reviewed the literature on food and sugar addiction and considered the evidence suggesting the addictiveness of highly processed foods, particularly those with high sugar content. They looked closely at the addictive potential of sugar by contrasting evidence from the animal and human neuroscience literature on drug and sugar addiction. 

They found very little evidence to support sugar addiction in humans, and findings from the animal literature suggest that addiction-like behaviors, such as bingeing, occur only in the context of intermittent access to sugar. These behaviors likely arise from intermittent access to sweet tasting or highly palatable foods, not the neurochemical effects of sugar [11].

Other researchers conducted a large-scale study in 1,495 university students in which they examined whether foods mainly containing sugar in particular might cause 'addiction-like' problems that meet clinical Diagnostic and Statistical Manual of Mental Disorders (DSM) criteria for substance dependence, and, also whether in turn this relates to body weight and negative affectivity (i.e., depressed mood). 

These findings indicated that sugary foods contribute minimally to 'food dependence' and increased risk of weight gain. Instead, they are consistent with the current scientific notion that food energy density, and the unique individual experience of eating, plays an important role in determining the reward value of food and promoting excessive energy intake [12].

In addition; some have argued that many of the tools used to evaluate addictive-like eating behaviors rely on self-assessment and reports from people participating in the study, which they argue leaves too much room for subjective misunderstandings [13].  

Are there certain carbs that are more addictive than others?

Researchers at Yale developed the Yale Food Addiction Scale (YFAS) in order to provide a validated measurement tool to assess addictive eating behaviors [14].

Scientists from the University of Michigan and the New York Obesity Research Center used the YFAS scale to measure addiction-like eating behaviors in students.  They used a cross-section design in their research and proposed that highly processed foods share pharmacokinetic properties (e.g. concentrated dose, rapid rate of absorption) with drugs of abuse, due to the addition of fat and/or refined carbohydrates and the rapid rate the refined carbohydrates are absorbed into the system, indicated by glycemic load (GL).

Glycemic load is a measure that considers both the GI of a food as well as its portion size. When compared to GI, GL is typically a more accurate measure of how a food impacts blood sugar level.

They stated that the data provides preliminary evidence that not all foods are equally implicated in addictive-like eating behavior, and highly processed foods, which may share characteristics with drugs of abuse (e.g. high dose, rapid rate of absorption) appear to be particularly associated with "food addiction."[15] 

Can we overcome carb cravings?

Although evidence demonstrates that carbs display some addictive properties, there are many techniques you can use to overcome cravings for carbs and other junk foods.

One of the most powerful and empowering steps you can take to stop carb cravings is simply to plan for them ahead of time.

Having an action plan in mind for those moments when cravings hit may help you feel prepared and empowered to take a pass on carb-laden junk foods and make a healthier choice instead.

There is no right or wrong answer to this; the key is to take action. Different techniques may work better or worse for different people.

Here are a few practical recommendations and tips to prevent carb cravings: 

• Fill up on protein first. Both animal and vegetable sources of protein, including meat, eggs, tofu, and beans, are renowned for helping you have a feeling of satiety [16].
• Eat a piece of fiber-rich fruit. Fiber will help fill you up and its natural sugars may also help satisfy cravings for something sweet [17].
• Stay hydrated. There is some evidence suggesting that dehydration may trigger cravings for salt. Since many salty foods are also high in carbs, drinking water throughout the day may ward off cravings for both types of foods [18].
• Get moving and change your brain. Boosting your activity levels with steps, strength training, or any other exercise of your choice triggers the release of feel-good endorphins from your brain that might interrupt your carb cravings [19].
• Get familiar with your triggers. Get a clear understanding on which foods are hardest for you to avoid and prepare yourself to be around those trigger foods ahead of time.
• Take it easy on yourself. Nobody is perfect. If you give in to a carb craving, simply consider what you can do differently next time. Don’t beat yourself up over it. Just like anything else, learning to navigate carb cravings takes practice.

In Summary

Carbs are an essential macronutrient and are your body’s primary source of energy.

Some carbs, such as the low energy (fruits, vegetables), and high energy (whole grains), are extremely healthy. Other carbs can be incredibly processed and high in salt, sugar, and fat.

Early research on carbs; especially animal research suggest that they might display addictive-like properties. It’s pretty clear that they appear to stimulate certain parts of the brain and even influence the types and amounts of chemicals your brain releases.

Much more rigorous research, especially in humans is needed to uncover exactly how these mechanisms in the brain are affected by carbs.

Some of the most highly addictive carbs appear to be highly processed junk foods (i.e. pizza, chips, cakes, and candies).

If you struggle with carb cravings; there are various techniques mentioned above you can try to resist these cravings.  

References:

1. Hebebrand, J., et al., "Eating addiction", rather than "food addiction", better captures addictive-like eating behavior. Neurosci Biobehav Rev, 2014. 47: p. 295-306.

2. Finucane, M.M., et al., National, regional, and global trends in body-mass index since 1980: systematic analysis of health examination surveys and epidemiological studies with 960 country-years and 9.1 million participants. Lancet, 2011. 377(9765): p. 557-67.

3. Ahmed, S.H., K. Guillem, and Y. Vandaele, Sugar addiction: pushing the drug-sugar analogy to the limit. Curr Opin Clin Nutr Metab Care, 2013. 16(4): p. 434-9.

4. Lennerz, B.S., et al., Effects of dietary glycemic index on brain regions related to reward and craving in men. Am J Clin Nutr, 2013. 98(3): p. 641-7.

5. Larsen, T.M., et al., Diets with high or low protein content and glycemic index for weight-loss maintenance. N Engl J Med, 2010. 363(22): p. 2102-13.

6. Lustig, R.H., Fructose: metabolic, hedonic, and societal parallels with ethanol. J Am Diet Assoc, 2010. 110(9): p. 1307-21.

7. Lee, P.C. and J.B. Dixon, Food for Thought: Reward Mechanisms and Hedonic Overeating in Obesity. Curr Obes Rep, 2017. 6(4): p. 353-361.

8. Lennerz, B. and J.K. Lennerz, Food Addiction, High-Glycemic-Index Carbohydrates, and Obesity. Clin Chem, 2018. 64(1): p. 64-71.

9. Avena, N.M., P. Rada, and B.G. Hoebel, Evidence for sugar addiction: behavioral and neurochemical effects of intermittent, excessive sugar intake. Neurosci Biobehav Rev, 2008. 32(1): p. 20-39.

10. Avena, N.M., et al., After daily bingeing on a sucrose solution, food deprivation induces anxiety and accumbens dopamine/acetylcholine imbalance. Physiol Behav, 2008. 94(3): p. 309-15.

11. Westwater, M.L., P.C. Fletcher, and H. Ziauddeen, Sugar addiction: the state of the science. Eur J Nutr, 2016. 55(Suppl 2): p. 55-69.

12. Markus, C.R., et al., Eating dependence and weight gain; no human evidence for a 'sugar-addiction' model of overweight. Appetite, 2017. 114: p. 64-72.

13. Pressman, P., R.A. Clemens, and H.A. Rodriguez, Food Addiction: Clinical Reality or Mythology. Am J Med, 2015. 128(11): p. 1165-6.

14. Gearhardt, A.N., W.R. Corbin, and K.D. Brownell, Development of the Yale Food Addiction Scale Version 2.0. Psychol Addict Behav, 2016. 30(1): p. 113-21.

15. Schulte, E.M., N.M. Avena, and A.N. Gearhardt, Which foods may be addictive? The roles of processing, fat content, and glycemic load. PLoS One, 2015. 10(2): p. e0117959.

16. Leidy, H.J., et al., The role of protein in weight loss and maintenance. Am J Clin Nutr, 2015. 101(6): p. 1320S-1329S.

17. Hervik, A.K. and B. Svihus, The Role of Fiber in Energy Balance. J Nutr Metab, 2019. 2019: p. 4983657.

18. De Luca, L.A., Jr., et al., Water deprivation and the double- depletion hypothesis: common neural mechanisms underlie thirst and salt appetite. Braz J Med Biol Res, 2007. 40(5): p. 707-12.

19. Codella, R., I. Terruzzi, and L. Luzi, Sugars, exercise and health. J Affect Disord, 2017. 224: p. 76-86.