14 October 2009

The psychology of food cravings

Can't stick to your diet because you're constantly plagued by food cravings? You're not alone - many other dieters have the same problem. DietDoc analyses the psychology behind it.

You're trying hard to shake a few kilos, but endless cravings for anything from chocolate cake to cheeseburgers are hampering your efforts.

The good news is that you're not alone: many dieters complain that they can't stick to their diets because they're constantly plagued by food cravings that sabotage their resolve to stick to a weight-loss regimen. Others report that food cravings, particularly for sweet or fatty foods, are causing them to gain weight exponentially.

Two approaches
There are two major schools of thought relating to what causes, triggers and supports food cravings:

Behavioural scientists believe that food cravings are the product of psychological processes and factors, and that learnt behaviour plays an important role in the phenomenon of food cravings.

Biochemists, on the other hand, believe that some food cravings are caused by an imbalance in hormonal and chemical substances in the brain and nervous system, with particular emphasis on serotonin.

The psychology of food cravings
A variety of studies have centred on the psychological factors that may play a role in making us crave sweet and fatty foods. Let's take a look at some of the most interesting findings:

a) Chocolate cravings
Two studies concentrated on why people crave chocolate. One of the studies compared chocolate cravings in Spanish and American women with special emphasis on cravings experienced before the menstrual cycle. Craving chocolate is often strongest just before menstruation.

Interestingly, Zellner and co-workers (2004) discovered that the urge to eat chocolate before menstruation was stronger in American women than in Spanish women. These authors concluded that chocolate cravings have a cultural, rather than a psychological or physiological origin.

The second study by Gibson and Desmond (1999) found that hunger and a learnt response to satisfying this hunger by eating chocolate, played the most important role in chocolate cravings. In other words, individuals who often satisfy their hunger by eating chocolate, condition themselves to crave chocolate when they're hungry.

b) Mental images
Harvey and co-workers (2005) studied food cravings before and after their experimental subjects were asked to either imagine a food or a holiday scenario. Their results confirm that mental images of the desired food increase the tendency to overeat this food.

If you constantly fantasise about that delicious, smooth and creamy cake or chocolate, you'll be fuelling your cravings for these foods.

c) Binge eating
In another study conducted by Engelberg and co-workers (2005) 39 bulimic women were asked to monitor their eating episodes, periods of dietary restraint and binge cravings.

The results suggested that the periods of denying themselves food made the cravings worse. In other words, strict dieting was usually followed by binging on 'forbidden' foods. This is proof that unrealistic dietary restrictions can make dieters crave all the foods they're trying to avoid and therefore undermine their success.

It's far better and more sensible to use a balanced, moderately energy-restricted diet, combined with exercise, to lose weight, than to starve yourself. Periods of semi-starvation will just make the cravings worse.

d) Food deprivation
Polivy and co-workers (2005) at the University of Toronto investigated how 103 chocolate-deprived, vanilla-deprived or non-deprived female volunteers would react.

The chocolate-deprived group reacted by eating more chocolate than any other group. In addition, both groups who had to curb their intakes of 'forbidden' foods experienced more cravings than the non-deprived group.

The authors concluded that being deprived of certain foods, like chocolate, leads to cravings and overeating.

However, some studies found the opposite. A study performed at the University of Vermont by Harvey et al. (1993) with 93 obese type-2 diabetics, who either used a balanced low-calorie diet of approximately 1200 calories per day, or a very-low-calorie diet (400 calories per day) for 12 weeks, found that the latter group on the 'semi-starvation' diet experienced fewer food cravings than the former group.

A second American study (Martin et al., 2006), using very-low-calorie, supplement-based diets, confirmed that this diet caused less food cravings than standard low-calorie diets.

So, here we have two opposite views. Some researchers believe that deprivation of certain foods will make individuals crave these foods, while other researchers report that extreme dieting will reduce cravings.

When researchers present us with such different findings, we unfortunately can't get a clear-cut view of what's actually going on.

Additional studies may well pinpoint why there are differences. For example, it's possible that the use of very-low-energy diets (400 calories per day), which border on starvation and can't be recommended to the general population, do eliminate cravings.

However, the use of such extreme diets is restricted to individuals who require drastic measures to reduce their weight because of direct health threats. These diets can only be followed under the strict supervision of a medical team.

For those people who don't have to lose vast amounts of weight, a balanced, moderately-energy-reduced diet is still the better option, and as mentioned in the first study in this section, such diets may well lead to cravings.

e) Carbohydrate vs. protein deprivation
Most people are aware that there are two diametrically opposed approaches to slimming: the Atkins-type high-protein, zero-carbohydrate diets, and low-fat diets that permit users to eat plenty of carbohydrates and some protein.

A study conducted in Toronto (Coelho et al., 2006) demonstrated that experimental subjects who were carbohydrate-deprived (like dieters who use a high-protein, zero-carbohydrate diet) tended to develop cravings for carbohydrate-rich foods. On the other hand, the subjects who were protein-deprived didn't develop cravings for protein foods.

These results indicate that human beings need carbohydrates if we're to function without cravings. This is understandable when we keep in mind that carbohydrates are our best source of rapidly available energy. Cutting out carbohydrates is, therefore, a recipe for creating carb cravings and isn't advisable.

The latest research studies on the psychology of food cravings indicate that learnt responses and deprivation of certain foods, particularly carbohydrates, can fuel cravings and sabotage weight-loss attempts. Apparently, very-low-energy diets such as those used to treat massively obese patients under strict supervision, lessen cravings, but are not for general use.

Compared to high-protein Atkins-type diets, which exclude most carbohydrates, a high-carbohydrate diet with a moderate protein content will cause fewer cravings and make it easier to stick to dieting.

f) Eating breakfast
Jakubowicz and co-workers (2008) from the Virginia Commonwealth University in the US have found that eating a breakfast packed with both carbohydrates and lean protein, and even a small piece of chocolate, can help lessen cravings and hunger during the rest of the day. They also found that this can lead to significant weight loss.

In the study of 94 obese, sedentary women with metabolic syndrome, half were told to eat the big breakfast diet containing about 1240 calories, while the other half ate a 1085-calorie high-protein, low-carbohydrate diet for eight months.

At the end of the eight months, those on the more restrictive low-carb diet lost an average of almost 9 pounds (just over 4kg). But those on the big breakfast diet lost nearly 40 pounds (18kg). Additionally, those on the big breakfast plan reported feeling less hungry and had fewer carbohydrate cravings.

– (Dr Ingrid van Heerden & HealthDayNews, updated September 2008)

(Available on request)

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