GL Scientific Evidence

  • 7 Jul 2015
  • Reading time 6 mins
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“Substantial and consistent scientific evidence of the highest quality shows that a Low GL diet is more effective than conventional low fat or low carb diets, causes more weight loss on the same calories, reduces hunger and sugar cravings, is easy to maintain and good for your health.” Scientific Advisory Board on Weight Management

“Substantial and consistent scientific evidence of the highest quality shows that a Low GL diet is more effective than conventional low fat or low carb diets, causes more weight loss on the same calories, reduces hunger and sugar cravings, is easy to maintain and good for your health.” Scientific Advisory Board on Weight Management

This review documents the evidence that:

     
  • A Low GL diet is most effective for weight loss - more so than low calorie, low fat diets or high protein, low carb diets
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  • A low GL diet causes more weight loss on the same calories – by positively affecting metabolic rate
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  • A low GL diet is easy to maintain - by reducing hunger and craving for sweet foods
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  • A low GL diet is good for your health - creating rapid improvements in cardiovascular health and blood sugar control, and long-term reduced risk for cardiovascular disease, diabetes and cancer.

 See the evidence for yourself (last updated 2015)

Background

Obesity is Wide Spread

     
  • One in two people in Britain are overweight
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  • One in five are obese
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  • Obesity costs the NHS close to £1 billion
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  • Obesity causes 30,000 premature deaths
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  • Obesity is responsible for over 20 million working days lost per annum and 40,000 lost years of working life
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  • 1,000 people in Britain become obese every day

A brief history of losing weight

Weight loss diets as we know them started with the discovery of calories. The ability to measure the energy inherent in a food as calories led to the equation that one’s weight was the net result of calories consumed from food, less calories expended by exercise/activity and the body’s own metabolic needs, called the metabolic rate. Since fat has more calories per gram (9kcals per gram) than protein or carbohydrate (3.75cals for protein, 4kcals for carb) original weight loss diets were low calorie, low fat diets – examples of which are Rosemary Conley’s, Weight Watchers, and Slimming World. Despite the emphasis on low fat, low calorie diets over the past two decades the percentage of people overweight and obese has steadily risen.

Increasing interest in carbohydrates as a cause of obesity arose from three findings. First, that low blood glucose levels are the primary trigger of hunger and hence eating. Secondly, that only carbohydrate, not protein or fat, has a significant effect on altering blood glucose levels. Thirdly, that the incidence of overweight and obese people in the population has continued to rise despite decreasing calorie and fat intake and increasing exercise.

Government statistics show that the amount of calories we eat has steadily decreased over the last 15 years, while the percentage of obese people has steadily increased.  In addition, the 1998 Health Survey for England estimated that women increased their level of physical activity between 1994 and 1998, from 22 to 25 per cent, for men it seems there has been little change. Conversely, carbohydrate, and more particularly sugar intake, has also risen in line with increasing obesity.

These findings led to a different weight loss strategy involving high protein and low carbohydrate. Examples of which are the Atkins Diet. Such diets have proven, in many cases, slightly more effective than low calorie low fat diets, largely due to reducing appetite by stabilising blood sugar. However, their long-term results are not impressive, often due to poor compliance, a product of unnecessary over-restriction of carbohydrates. Their long-term effect on health is also questionable.

Increasing awareness that not all carbohydrates affect blood sugar in the same way led to the creation of the Glycemic Index of foods. The Glycemic Index or GI of a food is a measure of how quickly the sugars within a food raise blood sugar, and for how long they remain elevated, compared to glucose which is the body’s direct fuel source. This led to diets based on eating more low GI foods and less high GI foods as a means to control appetite and weight.

Why GL is more accurate than GI

Diets based on eating low Glycemic Index (GI) foods have a major problem. They are unquantifiable since the GI of foods only tells you about the quality of the sugars in a food in respect of raising blood sugar levels. The GI score tells you nothing about the quantity of carbohydrate within a food. (For example, both carrots and chocolate contain similar high GI, fast-releasing sugars and therefore share the same GI score. However, carrots contain a fraction of the amount of available carbohydrates compared to chocolate. Hence, you would need to eat a lot more carrots to end up with the same effect on your blood sugar levels.)

By knowing both the quantity of carbohydrates eaten and the GI of the food in question the total Glycemic Load (GL) of a diet can be determined. Low GI diets are therefore only crude indicators of benefit for low Glycemic Load (GL) ......

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