THE “CALORIE-NEGATIVE” DIET
FOODS THAT CAUSE OUR BODIES TO BURN MORE CALORIES TO DIGEST THAN THEY PROVIDE? SOUNDS TOO GOOD TO BE TRUE!
WORDS BY DR KELLIE BILINSKI, ACCREDITED PRACTISING DIETITIAN
According to popular belief, the amount of calories it takes to digest certain foods, such as celery, lettuce, cucumber, cabbage, asparagus, chilli, grapefruit and papaya, is actually more than the amount of calories in the foods themselves.
So the theory goes: if you eat 100 calories worth of food that takes 150 calories to digest you’ve burnt an additional 50 calories…sounds impressive. So if you simply eat kilos worth of these sorts of foods you’ll lose weight? Where do we sign up?
Unfortunately, it’s not that simple. Let’s look at it practically. In order to consume 100 calories worth of celery (which
contains 16 calories per 100g) you’d need to consume over 600g of celery! A few sticks of celery weigh about 100g, so if you eat a typical serve you’re really only burning an extra 8 calories for every serve.
THE GOOD NEWS
On the other hand, fruits are higher in calories due to their natural fruit sugar content, so it’s quite easy to consume excess calories if large quantities of fruit are eaten. For example, papaya contains approximately 42 calories per 100g so the calories can add up quite quickly, and the amount of extra energy supposedly burnt is also unlikely to be significant.
There are no scientific studies that actually show that this is true. However if it were true, lets put it into the context of meaningful weight loss. In order to lose a kilogram of fat in a week, you would need to burn an extra 9,000 calories. So burning an extra eight or so calories in a typical serve of food is really quite insignificant.
THE FOODS YOU SHOULD EAT
That’s not to say these sorts of foods, which are usually quite high in fibre and water content, have no value as part of an eating plan aimed at losing weight. These foods help to fill us up and increase satiety, which can reduce the likelihood of excess calories being eaten later on. In addition, many of the so-called calorie-negative foods contain important nutrients such as antioxidants and vitamins, all of which are essential for health.
Proponents of the negative calorie diet also claim that lean meats such as pork, turkey and chicken make the digestive
system work harder, temporarily boosting your resting metabolic rate, which in turn helps you burn more calories. Although it is true that our body takes more energy to digest proteins than it does to digest carbohydrates, in terms of weight loss, it’s not going to be significant. On the plus side, lean meats and meat alternatives are an excellent source of protein, which has been shown to keep you fuller for longer and prevent that energy slump and midmeal snacking later in the day.
WHY VARIETY WORKS
These sorts of fads are often short-lived. While many people start off enthusiastically, eating so much celery, cucumber and so on (or a social occasion where these foods aren’t the focus), can’t be maintained and inevitably leads to failure. As soon as someone returns to his or her normal eating habits, the weight returns.
These sorts of diets are difficult to follow over the long term for several reasons, including that they’re often quite restrictive. And the reality is that many of us would soon get to the stage where we could n’t face another celery stick! This is not to say that vegetable stick s and fruits are unhealthy – they’re a very good choice as a snack when eaten in the context of a balanced diet.
The problem with following these sorts of extreme diets that are restrictive or promote eating limited or excess amounts of particular foods is that they may cause you to miss out on other important nutrients such as protein, calcium, iron and other vitamins and minerals.
It is important that a healthy diet consist of a variety of foods from each of the five food groups every day. The Australian Dietary Guidelines recommend including at least five serves of vegetables, legumes and beans; two serves of fruit; wholegrain breads and cereals; lean meat, chicken, fish, eggs, nuts and seeds; and milk, yoghurt, cheese and dairy alternatives.
Unfortunately there’s no magic bullet. The key to successful weight loss is adopting a healthy lifestyle that leads to a calorie deficit. This means that more calories should be expended in daily activity and exercise than the amount eaten.
Any weight loss plan must be based on a balanced diet that meets your nutrient needs, fits your lifestyle and teaches you how to maintain your weight over the long term.
ABOUT THE AUTHOR: Dr Kellie Bilinski is an Accredited Practising Dietitian. Accredited Practising Dietitians are university qualified health professionals who are able to individually assess your diet and develop an eating plan that will allow you to lose weight, without risking your health. Visit the ‘Find an APD’ section of the Dietitians Association of Australia website at www.daa.asn.au to find an APD in your area.