Blaming the Brain on Weight Gain

Many people claim they are addicted to food. That may not be too far from the truth.

Over millions of years of evolution, our brains have adapted to provide us a reward for successfully ingesting food. The hormone dopamine appears to be the key link in this reward process. But to complete the circuit, dopamine has to interact with its receptor. It has been known for many years that the ability of dopamine to combine with one of its receptors (the D2 dopamine receptor) is compromised in obese individuals compared to normal-weight individuals (1). This led to the hypothesis that obese individuals overeat as a way to compensate for the reduction in the dopamine reward circuits just as individuals with addictive behaviors (drugs, alcohol, gambling, etc.) do when their dopamine levels are low. It is also known that food restriction up-regulates the number of D2 receptors (2). This likely completes the reward circuit.

This effect of increasing D2 receptors is confirmed in obese patients who have undergone gastric bypass surgery that results in calorie restriction (3). This may explain why gastric bypass surgery is currently the only proven long-term solution of obesity. More recent studies with functional magnetic resonance imaging (fMRI) have indicated that unlike women with a stable weight where the mere visual image of palatable food increases the reward activity in the brain, that response is highly reduced in women who have gained weight in the past six months (4). This suggests that the dopamine reward circuits are compromised in women with recent weight gain, thus prompting a further increased risk for overeating in those individuals to increase dopamine output.

So does this mean that the obese patient with a disrupted dopamine reward system has no hope of overcoming these powerful neurological deficits? Not necessarily. There are a number of dietary interventions to increase the levels of dopamine and its receptors. The first is calorie restriction, which is only possible if you aren’t hungry. The usual culprit that triggers constant hunger is a disruption of hormonal communication of hunger and satiety signals in the brain. It has been shown that following a strict Zone diet can quickly restore the desired balance that leads to greater satiety (5-7). The probable mechanism is the reduction of cellular inflammation by an anti-inflammatory diet (8-10).

Another dietary intervention is high-dose fish oil that has been demonstrated to both increase dopamine and dopamine receptors in animals (11,12). This would explain why high-dose fish oil has been found useful in the treatment of ADHD, a condition characterized by low dopamine levels (13). Finally, high-dose fish oil can reduce the synthesis of endocannabinoids in the brain that are powerful stimulators of hunger (14).

I often say that if you are fat, it may not be your fault. The blame can be placed on your genes and recent changes in the human food supply that are changing their expression, especially in the dopamine reward system. However, once you know what causes the problem, you have the potential to correct it. If you are apparently addicted to food, the answer may very well lie in an anti-inflammatory diet coupled with high-dose fish oil.

References:

1. Wang GJ, Volkow ND, Logan J, Pappas NR, Wong CT, Zhu W, Netusil N, and Fowler JS. “Brain dopamine and obesity.” Lancet 357: 354-357 (2001).
2. Thanos PK, Michaelides M, Piyis YK, Wang GJ, and Volkow ND. “Food restriction markedly increases dopamine D2 receptor (D2R) in a rat model of obesity as assessed with in-vivo muPET imaging and in-vitro autoradiography.” Synapse 62: 50-61 (2008).
3. Steele KE, Prokopowicz GP, Schweitzer MA, Magunsuon TH, Lidor AO, Kuwabawa H, Kumar A, Brasic J, and Wong DF. “Alterations of central dopamine receptors before and after gastric bypass surgery.” Obes Surg 20: 369-374 (2010).
4. Stice E, Yokum S, Blum K, and Bohon C. “Weight gain is associated with reduced striatal response to palatable food.” J Neurosci 30 :13105-13109 (2010).
5. Ludwig DS, Majzoub JA, Al-Zahrani A, Dallal GE, Blanco I, and Roberts SB. “High glycemic-index foods, overeating, and obesity.” Pediatrics 103: E26 (1999).
6. Agus MS, Swain JF, Larson CL, Eckert EA, and Ludwig DS. “Dietary composition and physiologic adaptations to energy restriction.” Am J Clin Nutr 71: 901-7 (2000).
7. Jonsson T, Granfeldt Y, Erlanson-Albertsson C, Ahren B, and Lindeberg S. “A paleolithic diet is more satiating per calorie than a mediterranean-like diet in individuals with ischemic heart disease.” Nutr Metab 7:85 (2010).
8. Pereira MA, Swain J, Goldfine AB, Rifai N, and Ludwig DS. “Effects of a low glycemic-load diet on resting energy expenditure and heart disease risk factors during weight loss.” JAMA 292: 2482-2490 (2004).
9. Pittas AG, Roberts SB, Das SK, Gilhooly CH, Saltzman E, Golden J, Stark PC, and Greenberg AS. “The effects of the dietary glycemic load on type 2 diabetes risk factors during weight loss.” Obesity 14: 2200-2209 (2006).
10. Johnston CS, Tjonn SL, Swan PD, White A, Hutchins H, and Sears B. “Ketogenic low-carbohydrate diets have no metabolic advantage over nonketogenic low-carbohydrate diets.” Am J Clin Nutr 83: 1055-1061 (2006).
11. Chalon S, Delion-Vancassel S, Belzung C, Guilloteau D, Leguisquet AM, Besnard JC, and Durand G. “Dietary fish oil affects monoaminergic neurotransmission and behavior in rats.“ J Nutr 128: 2512-2519 (1998).
12. Chalon S. “Omega-3 fatty acids and monoamine neurotransmission. Prostaglandins Leukot Essent Fatty Acids 75: 259-269 (2006).
13. Sorgi PJ, Hallowell EM, Hutchins HL, and Sears B. “Effects of an open-label pilot study with high-dose EPA/DHA concentrates on plasma phospholipids and behavior in children with attention deficit hyperactivity disorder.” Nutr J 6: 16 (2007).
14. Watanabe S, Doshi M, and Hamazaki T. “n-3 Polyunsaturated fatty acid (PUFA) deficiency elevates and n-3 PUFA enrichment reduces brain 2-arachidonylglycerol level in mice.” Prostaglandin Leukot Essent Fatty Acids 69:51–59 (2003).