Lucy has always battled with her weight and her body image. She reads every magazine article on losing weight, has tried every diet under the sun and avidly watches the fat content of everything she buys. Her kitchen cupboards are filled with 99% fat-free foods, she buys low fat milk and avoids fried food. Yet Lucy is still struggling with her weight and cannot seem to shift the excess body fat.

So many people, like Lucy, are working hard at trying to follow a low fat diet yet are not achieving their desired results. What is going on?

The food industry has responded by producing a mass of fat-free and fat reduced products. We even have fat-free or reduced-fat biscuits, chips, cakes, ice cream and even chocolate! Yet despite all this the low fat diet advice has not managed to curb the growing tide of overweight and obesity.

While some have questioned the efficacy of the low fat approach, I feel the problem lies in the way we have interpreted the message and applied it to our diets. The emphasis has been solely on reducing fat, which many have taken to the extreme and almost try to eliminate fat altogether from their diet (an impossibility), while little thought has been given to the quality of the remaining diet.

There is good evidence to support the low fat approach as a valid method for reducing body fat and controlling your weight but there are several points to watch out for. If you are not getting results with your approach, take a look at the following and rethink your eating plan to take these into account.

"I can eat as much as I like so long as its low fat!"

Low fat products lull us into a false sense of security - we view the food as fat-free and therefore healthy and almost energy-free. Consequently we eat far more of the low-fat product than we would have the full fat original.

Rather than 2 scoops of ice cream savoured and enjoyed, we have half the carton of the low-fat version or instead of 1 or 2 chocolate biscuits we have half a dozen if they say they are 95% fat free. It 's not hard to see that while you believe you are eating low fat, your energy intake has not been reduced and in fact your fat intake may still be considerable given the large quantity of food eaten.

For example regular potato crisps contain 9.7g fat per 100g while the `light' version contain 5.4g fat per 100g. If we compare a standard 25g serve of each, the regular crisps provide 2.4g fat and 38 Cals (158kJ) and the light version 1.4g fat and 30 Cals (124kJ). In other words eating exactly the same amount but choosing the light version of the snack saved 1g of fat and only 8 Cals (34kJ) - not a significant saving of fat or energy. Imagine now that you ate twice as many of the light versions, as they were after all low fat! You would have consumed 2.8g fat and 60 Cals (248kJ) - slightly more fat and far more energy than a small serve of the regular snack.

"Carbohydrates won 't make me fat"

Early research found that the enzymes involved in converting carbohydrates to fat for storage as body fat, were present in humans but the pathways seemed to be rarely used. This remains true under most circumstances - the carbohydrates that we eat are ultimately converted to glucose for use as a fuel by the body or stored as glycogen (a starch-like, long chain carbohydrate) for later use. Once carbohydrates are converted to fat they cannot be converted back to carbohydrate - plus the body wastes energy-converting carbohydrates to fat.

It is not therefore an efficient process and far preferable for the body to store or burn as much of the incoming carbohydrate as possible.

However the problem is that this message has been interpreted by many as saying we can eat as much carbohydrate as we like without getting fat. This is of course not true. The bottom line is the energy balance equation - if you eat the same amount of energy as you expend your weight will remain unchanged.

A low fat, high carbohydrate diet will therefore not help you to lose body fat unless it provides less energy than you are expending. Many of us may simply be eating way too much bread, pasta, potatoes, rice and low fat snack products than our energy requirements dictate. There is a limit to how much carbohydrate can be stored in the body -when we eat more than can be stored and used for immediate fuel needs, the carbohydrate has to go somewhere it cannot simply disappear and the body is forced to convert the excess carbohydrate into body fat for storage. Of course any fat that is
eaten will also be stored as body fat.

"All carbohydrates are the same"

While the entire focus has been on fat intake we have forgotten about the quality of the other nutrients in the diet. All carbohydrates are not the same and do not have the same physiological effects within the body. Some carbohydrate-rich foods are digested and absorbed very quickly, resulting in large and rapid rises in blood glucose and subsequently the hormone insulin. This may be counterproductive to weight control in two ways:

1.The large rise in blood glucose is followed by a rapid drop, often to levels below normal -this rapid decline in blood glucose seems to send a signal to the brain that more fuel is needed and stimulates further eating. If you have ever felt hungry a couple of hours after a low fat, high carbohydrate meal this may be why.

2. Continually pumping out more insulin than our bodies are designed to puts you more at risk of developing diabetes and heart disease. Insulin plays a crucial role in controlling blood glucose and in getting the nutrients from our food up into tissues for use around the body. However too much insulin may promote body fat storage and reduce fat burning. In this way eating too many of the wrong types of carbohydrates may be counterproductive to fat
burning.

The Glycaemic Index (GI) is designed to help you to select the best types of carbohydrate-rich foods. Foods with a high GI are those that give rise to large blood glucose responses - while these foods are beneficial for some such as athletes following heavy training, most of us should cut down on these foods.

Base your diet instead on low GI carbohydrate-rich foods. These will take longer to digest, help you feel fuller for longer and provide a steadier stream of energy for the body. In general less processed and refined carbohydrates have a lower GI (eg. most fruits and vegetables, multigrain breads, legumes, rolled oats, barley and pasta).

"I try to keep to less than 30g fat per day"

Counting fat grams is counterproductive to weight control firstly because it makes you obsess over food - exactly the opposite of what we are trying to achieve - and it does not take into account good and bad fats. Assessing a product or a food solely on its fat content means you are likely to be cutting out the good fats and losing out on essential fatty acids, fat soluble vitamins, antioxidants and important fats such as the omega-3 fats.

Low-fat diets have been recommended for weight loss for the last 20-30 years This as essentially based on three facts: 1. Fat is the most energy dense macronutrient with more than double the energy per gram of carbohydrate or protein (9 calories per gram of fat compared to 4 for protein and carbohydrate). It is therefore easy to overeat on fat-rich foods. 2. Dietary fat is easily stored as body fat, whereas it is an inefficient and energy losing process to convert carbohydrate or protein to body fat for storage. 3. Fat seems to be the least satiating macronutrient and therefore curbs our appetite less than carbohydrate or protein-rich meals.

Conclusions

Reducing the fat intake of your diet remains a valid approach to eight control but we need to think beyond the fat issue and consider the total quality of our diet. Try to stop obsessing over the fat content of foods and instead think of quality - quality of the fat, carbohydrate and protein present. Changing the type of fat that you are eating is far easier to do and stick with than trying to eliminate fat completely - together with choosing quality low GI carbohydrates, lean protein sources and plenty of fruit and vegetables.

Consider the total amount of food that you are eating - eating a better balance of carbohydrate, protein and fat may help you to be relaxed about eating and consequently eat less. All in all choose quality rather than quantity and you will be back on the road to success.

(C) Penny Hunking, 2002 (originally published in 'EAT' Magazine)

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Useful links:

Energise.co.uk Penny Hunking's website.

GlycemicIndex.com for more on GI and ratings of foods.