Eating is not a rational behavior. Eating is not like studying for a test, memorizing facts, understanding and manipulating sophisticated mathematical equations, painting a portrait or writing a book. It is not an advanced behavior, but a primitive one—one that is instinctual, hard-wired and in many ways uncontrollable. Humans are endowed with a metabolic pathway that allows them to store extra energy as fat. One might argue the existence of a pathway to create and store energy means that people were actually designed to eat too much. Given that more food is available in today’s world compared to the past, individuals are functioning normally and responding in the manner in which they were designed. Nothing is wrong with us. The problem is the environment in which we now live.

Beginning in the 1960s, the green revolution increased the production of cereals, rice, wheat and maize—staples for much of the world. As a consequence, three major changes have occurred:

1. the relative price of food has declined, especially for high calorie foods filled with fat and sugar;

2. food is increasingly easily accessible; and

3. multi-national corporations have invested heavily in advertising and marketing to sell more of their products, making cues to eat more salient.

Together, these three changes have made it possible for people to eat as much as they can whenever they want, as well as making people eat too much, and artificially stimulating people to feel hungry when they do not need to eat.

Food prices

The increasing yields and production of all staples have led to lower food prices overall in relation to income,⁹ and in the United States, in 2006, the average family spent only 9.9% of their income on food compared to 14.8% 40 years earlier and nearly 25% in the 1920s.¹⁰ Interventions that have manipulated the price of food have shown that when healthier foods are less expensive people are more likely to buy them.^11–13 Another study, examining the incidence of obesity in elementary school children, showed that in communities where the cost of meat was high and vegetables were low, children were less likely to become overweight than in communities where meat prices were low and fruits and vegetables were high.¹⁴ People are sensitive to price, and when food is cheap, they are able to purchase more. When high-calorie foods are cheaper than lower-calorie foods, more people purchase and eat too many calories.¹⁵

Food accessibility and portion sizes

Another dramatic change in the food environment has been the increase in portion sizes. Portions for beverages in 6 oz and 8 oz sizes, for example, are no longer sold in the US, in favor of 12 oz, 16 oz, 20 oz and larger sizes. The typical American restaurant now serves portions that are 2–5 times in excess of what indi viduals typically require to stay in energy balance.^16–18 Beyond portion sizes, the number of places that now sell food has also increased dramatically. While the number of convenience stores and restaurants has increased dra matically, especially fast-food restaurants, a large proportion of non-restaurant outlets such as supermarkets and businesses that previously did not sell prepared food now do. Food that you can eat right away (“convenience food” —especially candy, cookies, chips and sodas) can be purchased in book stores, car washes, hardware stores and even building supply warehouses. One survey of multiple cities estimated that about 40% of non-food outlets in the United States now sell food (personal communication, Tom Farley, February 2008). Furthermore, the availability of vending machines has multiplied several times over the last couple decades,¹⁹ and these machines now sell food in office buildings, public buildings, parks, petrol stations—practically anywhere. And the types of food items sold are predominantly high-calorie salty snacks (e.g., chips), cookies, candy and sugar-sweetened beverages.

Food advertising—cues

Along with increased food availability is the massive increase in advertising and marketing for food products. The amount of funds spent on commercial advertising and marketing research exceeds funds available for nutrition education more than 10-fold.^20–22 Further, the sophistication of advertising and the ability to target subgroups has advanced substantially. Some studies investigating the differential exposure to age, race and ethnic groups indicate that children and racial ethnic minorities are differentially targeted to receive a high proportion of food advertising not only in television, but in magazines as well.²³ Tirodkar and Jain compared the number of commercials shown on prime-time shows with African American characters to prime-time shows with predominantly white characters.²⁴ Not only did the shows targeting African Americans air 66% more commercials about food (4.8 spots for a 30-minute show vs 2.9 advertisements for white audiences), but the advertisements shown to the African-American audiences were more likely to promote unhealthy items. For example, 30% of the food commercials for African American audiences were about candy and chocolate whereas there were only 14 % for white audiences; 13% advertised soda during Black prime time as opposed to only 2% for white audiences.²⁴ Given that studies indicate that exposure to food advertisements influence food preferences, this level of exposure could explain, in part, the health disparities seen among racial and ethnic minorities.²⁵

Automatic responses to the food environment

Understanding the way in which humans respond to environmental stimuli is critical to identifying how the dramatic changes in the food environment have been able to transform the eating behavior of Americans, and is now quickly influencing people across the entire globe. People are hardwired to respond automatically to food and images of food. These responses are immediate and the physiological reflexive responses are largely uncontrollable. For example, when people are exposed to images of appetizing food, their brains automatically and reflexively secrete dopamine, activating at least five separate reward centers in the brain.²⁶ This activation leads to food cravings. The physiological pathway involving dopamine excretion in response to food images involves the same neural pathways that are associated with drug addictions.²⁷ The magnitude of the arousal of the reward centers varies considerably across individuals and is believed to explain the variability of drives for food, hyperphagia and obesity.²⁶ Given that food advertising and food availability have mushroomed, people are being artificially stimulated throughout the day to feel hungry and crave food.

Limited ability to exercise control

Not only are people unable to prevent the automatic, reflexive responses to food images and foods (including salivation), but it may be difficult for many people to distinguish between artificially induced hunger and desire for food and true hunger that comes from a low blood sugar. Moreover, people may be unable to recognize that they are being artificially stimulated to feel hungry, since many of the cues are imperceptible.²⁸ Humans have the ability to perceive images through visual systems that are not perceived by the part of the brain that provides conscious awareness.^29,30 Although this type of stimulation may occur during a small proportion of the time, it does not require much for individuals to be out of energy balance. Large amounts of calories are available in small volumes of food; a small candy bar has over 200 calories. Relatively small amounts of calorie excess are believed to be fueling the obesity epidemic.³¹

Evidence that people can be stimulated to eat too much without their awareness or insight comes from a variety of studies. In one study, subjects exposed to subliminal images that were unrelated to food, were influenced to drink a greater quantity of an energy drink, and rate it more favorably. They had no subjective awareness that their behavior was affected in the least.²⁹

Another study that showed people lacking insight into the quantity of food consumed was demonstrated when subjects were provided with soup in self-refilling bowls. Without cues that let people judge quantity, subjects ate 73% more than the participants given soup in normal bowls, yet did not feel more satiated.³² People also have a limited capacity to judge volume and portion sizes. In several studies, individuals were unable to correctly judge the volume held by two glasses of different shapes and incorrectly thought that a tall narrow glass held more liquid than a short wide glass.^33,34 Since people do not have any internal signals that allow then to regulate the quantity of food to eat,^3,35 they rely on external cues, such as portion sizes, to determine how much to consume.

People usually consume more calories than they need to when offered too many, and they do not compensate for the excess by eating less at subsequent meals.^36–39 Instead, excess calorie consumption initiates the pathway to store excess energy as fat. People cannot easily judge when this happens.

Studies in the field of behavioral economics indicate that individual choices are strongly influenced by the means through which the choices are presented.⁴⁰ People exercise a limited amount of cognitive decision making, and typically rely on specific heuristics to make decisions, particularly when they are overwhelmed by too much information or are under stress. In these cases, people rely on default, impulsive reactions, rather than considered cognitive decision making.^41,42 Heuristics governing food choices have more to do with factors such as price, convenience and emotional associations rather than concerns about health.

A wide variety of interventions are likely to be successful if they address our natural proclivity to be attracted to food, to be stimulated to feel hungry when confronted with food cues (regardless of how full we are), and to maximize the quantity and variety of food we eat. The following are be discussed:

• price incentives
  
• regulating portion sizes and labeling calorie information
  
• counter-advertising campaigns
  
• controlling food cues
  
• regulating food accessibility.

There is limited evidence for the effectiveness of these interventions, since they have never been tried on the scale needed to have an impact. Given that these would address pathways shown to be causally related to overconsumption, they are, nevertheless, the most promising.

While regulating the food environment may seem heavy handed, what people fail to appreciate is how much it is currently being engineered so that people will automatically eat more than they need, eat more unhealthy foods than they should, and, as a consequence, develop chronic diseases that shorten their lifespan. The limitations of human cognition make it very difficult for people to have insight into the process. People cannot naturally identify which nutrients and calorie amounts are present in specific foods, particularly those that are processed and transformed from raw ingredients, nor can they prevent being artificially stimulated to desire foods that are high in sugar and fat. Thus, there is a role for government to regulate the food environment so that people will automatically have the optimal quality and quantity of food available for them to choose.

Regulating prices

Currently, unhealthy foods like salty snacks, cookies and candy and sugar-sweetened beverages are less expensive per calorie than healthier foods such as fruits and vegetables.^43,44 Taxing the unhealthy foods and subsidizing the healthy ones has been proposed, and has been implemented in a very minimal way in several states in the USA.⁴⁵ However, the fact that people are very price sensitive when it comes to food purchases, suggests that this is a promising approach. There is enormous scope for adding taxes to unhealthy foods, which could be used to subsidize healthy ones.

Labeling and regulating portion sizes

We will be able to control our weight when the food environment is one that does not artificially make us hungry, that automatically provides the variety of foods that we need, and that limits the accessibility of the foods that make us sick. Needless to say, the changes required would precipitate a multitude of barriers and opposition, because many companies would stand to lose profits from the sales of food that are making people sick. Making the necessary changes would require political genius and indefatigable will-power and conviction.

Since eating is largely an automatic behavior, the current situation that requires each and every person to think very carefully and control what they eat in order not to gain weight constitutes an undue burden and is likely to interfere with our abilities to do other things. Given that the majority of people are over-weight, this burden is too much for most of us. In fact, many people on diets suffer from a loss of executive functioning and impaired decision making.⁵² Our thinking power is best devoted to solving everyday problems with our jobs, our friends, our homes, our families and our plans for the future. Most people do not have the spare cognitive capacity to count every last calorie, vitamin and mineral. If we want a diet that promotes optimal health, people will need a lot of help. Just as we make sure the water that is available is safe to drink, the food that is available should also be safe, provided in the appropriate quantities for every person, neither too much nor too little. We just have to accept the fact that it is too hard for most individuals to do this on their own.

1 Cutler DM, Glaeser EL, Shapiro JM: Why Have Americans Become More Obese? Cambridge: National Bureau of Economic Research, 2003.

2 Davey RC: The obesity epidemic: too much food for thought? Br J Sports Med 2004; 38 (3):360–363.

3 Levitsky DA: The non-regulation of food intake in humans: hope for reversing the epidemic of obesity. Physiol Behav 2005; 86 (5):623–632.

4 Zhang L, Rashad I: Obesity and time preference: the health consequences of discounting the future. J Biosoc Sci 2008; 40 (1):97–113.

5 van den Bos R, de Ridder D: Evolved to satisfy our immediate needs: self-control and the rewarding properties of food. Appetite 2006; 47 (1):24–29.

6 Sharma M, Wagner DI, Wilkerson J: Predicting childhood obesity prevention behaviors using social cognitive theory. Int Q Community Health Educ 2005; 24 (3):191–203.

7 Fuentes-Afflick E, Hessol NA: Acculturation and Body Mass among Latina Women. J Womens Health (Larchmt) 2008; 17 (1):67–73.

8 Koya DL, Egede LE: Association between length of residence and cardiovascular disease risk factors among an ethnically diverse group of United States immigrants. J Gen Intern Med 2007; 22 (6):841–846.

9 Khush G: Productivity improvements in rice. Nutr Rev 2003; 61 (6 Pt 2):S114–S116.