Nicholas Freudenberg reviewed two books on obesity in the Lancet this week: “The End of Overeating: Taking Control of the Insatiable Appetite” by David Kessler and “The Evolution of Obesity” by Michael Power and Jay Schulkin. From his description they look like they are worth reading. He then went on to discuss how the global food industry contributes to obesity. It is certainly true that the goal of the food industry is to sell us products. What is interesting here is the question of motivation and of responsibility. As a free people do we not have a responsibility to understand how our behavior affects us? Do not corporations have a responsibility to avoid selling us dangerous products? The motivation of the food industry is simple: profit. Our motivations are quite a bit more complex. We eat for fuel but also for comfort. No one should deny the emotional power of the brownie; the consolation of mac and cheese.
The downfall of big tobacco was not just that some people who smoked got lung cancer or chronic obstructive pulmonary disease but that the companies deliberately formulated their product to maximize addiction. Can the same be said for the food industry? Indeed at a recent convention of the Confectioners Association and Chocolate Manufacturers Association, Susan Smith, an official of the Association stated that “They are looking at the tobacco model, turning their sights on sugar the same way they did on tobacco”. If we can become addicted to sugar it would have far reaching consequences. Think about dieting. When the cocaine addict goes off the drug, he or she undergoes intense withdrawal symptoms that are not just psychological but physical. Does a dieter go through milder but ultimately similar physiological changes? It would certainly explain why dieting is so hard and why so many fail at the attempt. The legal system is salivating over the possibilities (another addiction problem I suspect).
A search for the terms “addiction” and “sugar” in the National Library of Medicine pulled up 451 peer-reviewed papers as of this writing. Clearly there exist a number of researchers who think the two terms should be linked. But, addiction is a loaded term. Researchers use the word in very specific ways which may or may not correlate with what we think of as a lay public. When we use the cocaine or heroin model as an example of addiction we are considering a state of physical dependence. In turn, psychiatrists consider addiction as a state of compulsion where the patient pursues a behavior no matter how detrimental it is to the rest of his or her life. While these two states overlap they are not synonymous.
Addiction circuitry associated with dependency has been mapped and central to this circuitry is the nucleus accumbens. A nerve tract called the median forebrain bundle synapses within the nucleus accumbens and releases dopamine as well as endogenous opiates. We can give a rat heroin or cocaine and observe exactly the same changes in behavior and in physiology as we see in people. Turning to sugar, numerous laboratories have given rats the choice of a sugary food versus a non-sugary food and (no surprise) they chose the sugar. In other experiments where fat was substituted, again the rats chose the fat. Is this addiction? Perhaps. In the case of sugar, withdrawal was observed in the rats upon removal of the sugar but withdrawal was not observed with other carbohydrates or with fat. Then a group performed a clever twist on this experiment. They asked whether it was the sugar itself that caused the addictive properties or if it was the taste of the sugar. These are two very different things. Keep in mind, heroin addicts do not make heroin soufflés; they inject the stuff. When sugar was injected, the neurobiological changes that had been observed all went away. The rats were not addicted to the sugar per se. They were addicted to the sensation of eating sugar. Another issue is the timing of the sugar. When the rats were exposed to sugar intermittently and allowed to gorge, they developed the best examples of withdrawal. Constant access was not as successful at producing an addiction phenotype.
While addiction has been associated with the release of dopamine and opiate neurotransmitters within the nucleus accumbens we cannot simply associate the presence of these neurotransmitters with addiction. This is because many simply pleasurable activities also activate these circuits. This could involve winning a contest or simply looking at someone you love. However, we can distinguish between the firing of neurons associated with addiction (for example cocaine addiction) from the firing of neurons associated with a merely pleasurable experience if we use the right tools. In both rats and monkeys researchers, using electrophysiological techniques, were able to distinguish a pattern of neuronal firing that was different when the addicted animal was given a cocaine reward versus a food reward. The pattern seen with food rewards was the same for addicted and non-addicted animals. When constant exposure to sucrose was examined it elicited a pattern of neuronal activity that was far more similar to a pleasurable experience than addiction.
While the eating of sugar may simply be a pleasurable experience there is ample evidence that intermittent reinforcement is a very powerful modulator of behavior. Consider gambling casinos. Millions of dollars have been spent determining exactly the right rate of pay-out on slot machines to motive continued playing behaviors. Dog trainers know very well that by only giving a treat some of the time, their canine students perform far better than if they receive a treat each time they act appropriately upon their cue.
Putting this all together, it seems that there is a component of addiction but it is not the sugar or fatty food. Addiction may come instead through the way we eat the food. Ask yourself; have you ever binged on something for comfort after a really bad day? When food is cheap and ample and comforting, it is extraordinarily easy to travel down this dangerous road.
Returning our gaze to the food industry, are they then blameless? Freudenberg uncovers the smoking gun and it is portion size. Apparently, the size of prepared food portions has been growing steadily bigger over time. This makes little sense from the commercial point of view except that it caters to and encourages our need to binge. A friend of mine who recently became a diabetes educator told me that the biggest hurdle to overcome is the clean your plate mentality. When you have a pile of food on your plate, there is a strong sense that if you do not eat it all, you are wasting resources.
Dr. Freudenberg has presented a reasonable case for some degree of regulation. It will only help us if we help ourselves.