Go to Google Trends and search for diet. The spikes in the graph show a dramatic increase in Google searches for this word around the Christmas to New Year period each year. The heightened interest in weight loss should come as no surprise to those of us who enjoy the treats and festivities of this season. But in a society already saturated with rich food, over-indulgence is more than just a holiday issue.

The prevalence of obesity in modern western societies is widely acknowledged as one of the great healthcare challenges of our time. Yet the problem of obesity and diet is less of a mystery now than it has ever been. As the World Health Organisation states: "The fundamental cause of obesity and overweight is an energy imbalance between calories consumed on one hand, and calories expended on the other hand."

This is WHO-speak for: "eating too much and exercising too little."

Why do we eat too much, when it is clearly not in our best interests to do so? The simple answer is that we fail to recognise the point at which eating changes from a healthy, good action into an unhealthy, bad action. We miss this point because we have confused our motives for eating in the first place.

Most diets aimed at weight loss will encourage us to restrict either the amount of food we eat, or the type of food we consume. But these strategies play to the underlying flaw in our attitude to food. We are consumed by the desire for pleasure in eating.  Some diets will allow us to continue enjoying whatever foods we like, so long as we sacrifice quantity. Other diets will let us indulge our craving to eat as much as we like, so long as we restrict ourselves to certain low-calorie foods. Either way, a sacrifice is made so that some part of our appetite can still be fulfilled.     

These are dangerous approaches, because they inflame the very desires that encourage us to over-eat in the first place. It is the desire for the sensual pleasure of eating, which perverts our relationship with food and leaves us in mental and physical disorder.

Food serves two primary goods in human life. First, food gives us the strength and nourishment we need to grow and to move. Second, food serves a social or convivial function, as we offer hospitality to guests, or come together for shared meals. As with many other good things in life, it is tempting to add a third function of "providing pleasure". But this temptation to think of pleasure as a separate and distinct good or function is misguided and dangerous. Pleasure should instead be understood as our natural response to good things. Hence we find pleasure in the nourishment of food, and in the convivial sharing of food. But to seek pleasure for its own sake is to seek a subjective response quite apart from real goods. This pursuit of pleasure is the cause of numerous physical and psychological problems, as evidenced by the obesity epidemic.

Many people over-eat in the pursuit of pleasure for its own sake. Their actions betray a disordered motive as their consumption of food meets and then exceeds the good of nourishment, becoming instead a harm to their health and life. Many diets will fail to help such a person, because they do not recognise anything inherently wrong in eating primarily for pleasure. So instead of combating the wrong motive directly, many people find themselves locked in a psychological battle between the desire for pleasure and the desire for health. Typical dieting behaviours can succeed in this scenario, but behavioural change is made more difficult by the failure to understand that any amount of food consumed with primary consideration for the pleasure it brings, is food consumed in error and from a false and harmful motive.

This error is the essence of what we used to call "gluttony" -- the inordinate or disordered desire for food. The medieval theologian Thomas Aquinas wrote that: “The vice of gluttony does not reside in the substance of the food, but in the appetite ill-regulated by reason.”
 
If our appetite is regulated by reason, we will not seek to eat more than is necessary to nourish ourselves. Nor, as Aquinas points out, will we develop other manifestations of gluttony such as eating dishes that are too expensive, eating food too "daintily" or elaborately prepared, eating too soon, and eating too eagerly. These behaviours indicate an appetite that is detached from the rational purpose and order of eating.

It may seem overly strict or mean-spirited to speak of a "rational purpose" for eating.  But the truth is that our present society faces a crisis built on excess consumption in defiance of rational limits. It would be inadequate and somewhat perverse to merely extol specific caloric limits, or to contemplate "junk food" taxes or publicly funded lap-band surgery, when the root of the problem is our willingness to indulge an unhealthy appetite. 

In this writer's experience, the decision to eat only for nourishment was immediately challenged by a powerful craving for the pleasure of food.  My appetite felt cheated, as though I was being robbed of something -- not merely in terms of quantity (refusing a second serve) but in terms of satiety also. Eating according to my need for nourishment took away my freedom to revel in the sensory pleasure of food. This loss was keenly felt, both at the time of eating and on subsequent occasions when boredom would otherwise have suggested to me some form of snack. The sense of loss implies that the pleasure of eating has played a greater psychological role than I had expected.   

In the wake of this loss, I have seemed more sensitive to the difference between actual hunger and mere craving. This sensitivity can grow as soon as we begin to distinguish between actual needs in terms of nourishment, and mere craving based on the desire for pleasure.  Another benefit of this “ethicist's diet” is the growing sense of "detachment" from the pleasure of food.  We can still enjoy the taste of food, but the over-riding goal of nourishment prevents this enjoyment from becoming a fixation or future craving. This is, perhaps, closely linked to a third benefit of the ethicist's diet: a slowly strengthening discipline or temperance in the face of sensual pleasure. 

Aside from these personal changes in attitude and experience, the focus on nourishment leaves us with greater freedom to use food for the benefit of others. If nourishment is so easily achieved, then what is the point in great feasts, elaborate dinner parties, beautiful dishes, and food in great quantities?  The point is that we can use food in these forms as a way of giving to others. We can take pains to design and prepare wonderful meals without any thought of our own sensual pleasure, but merely to express our love and generosity to friends and family.

The focus on nourishment has also left me wondering what to do with my time, energy, and attention. This sense of detachment from the pleasure of food seems like it should be filled by something of greater importance. I have spent a long time revelling in my senses, feeding an appetite that ultimately leads nowhere and contributes nothing to my objective happiness and well-being. My goal in eating is now to nourish my life...so what is the goal of my life? If we now eat in order to live, we must surely begin to ask ourselves what we live for, if not the pursuit of satiety.

Zac Alstin works at the Southern Cross Bioethics Institute in Adelaide, South Australia.