If you're avoiding starchy foods such as bread, rice and pasta in an effort to shed a few pounds, you might consider adding them back to your meals -- providing that you choose the right ones.
In the latest study to compare the effects of four weight-loss diets, a high carbohydrate-low glycemic diet was the most effective at promoting fat loss and lowering blood cholesterol.
For the past decade, the debate over the best diet to lose weight has centred on carbohydrates.
Dietary guidelines advocate carbohydrates as the major source of daily calories (55 per cent) for the prevention of heart disease.
In 1992, Canada's Food Guide to Healthy Eating was revised to reflect an increase in the recommended servings of grain products (five to 12 a day), and vegetables and fruit (five to 10 a day).
But along with our increased carbohydrate intake we've also witnessed rising rates of obesity and Type 2 diabetes, both risk factors for heart disease -- an observation that has raised concern about the quality of carbohydrates we're eating.
A number of recent studies suggest that a lower-carbohydrate, higher-protein or low-glycemic diet is best, to lose weight and reduce the risk of heart disease. The glycemic index (GI) is a scale that ranks carbohydrate-rich foods by how quickly they are digested and raise blood sugar. (The ranking compares the food to pure glucose, which ranks 100.)
Foods that rank high on the GI scale (70 or higher) are fast acting: They're digested quickly, and, as a result, they cause large rises in blood sugar and insulin, the hormone that removes sugar from the blood and stores it in cells.
Examples of such foods include white and whole-wheat bread, baked potatoes, refined breakfast cereals, instant oatmeal, cereal bars, raisins, ripe bananas, carrots, honey and sugar.
It's thought that a diet based on high-GI carbohydrates is less effective at promoting weight loss because the large spikes in blood sugar and insulin it causes can trigger hunger and inhibit the breakdown of body fat.
Foods with a low GI value (less than 55) release sugar more slowly into the bloodstream and don't produce an outpouring of insulin. Examples include grainy breads with seeds, steel-cut oats, 100-per-cent bran cereals, oat bran, brown rice, sweet potatoes, pasta, apples, citrus fruit, grapes, pears, legumes, nuts, milk, yogurt and soy milk.
While the glycemic index tells you how quickly a particular food gets converted to blood sugar, it doesn't tell you how much carbohydrate is actually in that food.
For instance, if you eat a serving of food that contains only a small amount of carbohydrate, it won't have much impact on your blood sugar and insulin levels regardless of its GI rank.
So researchers use a measure called the glycemic load (GL), which takes into account a food's glycemic index and the grams of carbohydrate in one serving.
In the latest study, researchers from the University of Sydney randomly assigned 129 overweight or obese adults, aged 18 to 40 years, to one of four weight-loss diets for 12 weeks.
All four diets held fat at 30 per cent of total calories, fibre at 30 grams daily, and calories at 1,400 a day, for women and 1,900 for men.
The diets differed in the amounts of carbohydrate and protein they contained and in their glycemic load. Diet 1 was high carbohydrate (55 per cent of daily calories) and high GL; Diet 2 was also high carbohydrate but low GL; Diet 3 comprised high protein (25 per cent), moderate carbohydrates (45 per cent) and high GL; Diet 4 was similar to Diet 3, but had low GL.
After 12 weeks, all participants had lost weight, ranging from 4.2 to 6.2 per cent of body weight. That might seem modest, but a weight loss of 5 per cent of body weight has been demonstrated to reduce the risk of developing Type 2 diabetes by 58 per cent among overweight adults with impaired fasting blood sugar (a precursor to Type 2 diabetes).
The conventional Diet 1 (high carbohydrate, high glycemic) was associated with the highest blood sugar response and the slowest rate of weight loss. Overall, Diet 2 (high carbohydrate, low glycemic) outperformed the others in terms of losing body fat and lowering blood cholesterol. In the high-carbohydrate diets, lowering the glycemic load doubled the amount of body fat lost, but this did not occur in the high-protein diets. Diet 2 also reduced total and LDL (bad) cholesterol levels by 4 and 6 per cent, respectively; that was thought to be due, in part, to eating more fibre-rich foods. Diet 3, the high-protein, high-glycemic regime, actually increased LDL cholesterol by 8 per cent.
Thus it appears that the quality of the carbohydrates you eat can influence your weight, your blood sugar and your blood cholesterol. The following tips will help you replace high-GI foods with low ones without making drastic changes to your diet:
Replace refined breakfast cereals with ones based on oats, oat bran, wheat bran and psyllium.
Choose breads and crackers made with whole grains, stone-ground flour or sourdough.
Instead of white potatoes and white rice, choose barley, quinoa, sweet potatoes and pasta.
Use salad dressings made from vinegar or lemon juice; the acidity will result in a further reduction in the GI of your meal.
Avoid eating high-GI snacks such as pretzels, corn chips, refined crackers and rice cakes. Instead, choose fresh fruit, low-fat dairy products, nuts or plain popcorn.
Choose fruits that are more acidic (oranges, grapefruit, cherries, strawberries, green apples) as they have a low GI and will lower the glycemic load of a meal.
For more information about glycemic index and glycemic load, visit http://www.glycemicindex.com
Leslie Beck, a Toronto-based dietitian at the Medcan Clinic,
is on CTV's Canada AM every Wednesday. Visit her website