The Health Sciences Institute is intended to provide cutting-edge health information.
Nothing on this site should be interpreted as personal medical advice. Always consult with your doctor before changing anything related to your healthcare.

Effectiveness of a slow carb diet

Go Slow

Are you tired of hearing about low-carb this and low-carb that? No problem. Today I’m going to tell you about “slow-carbs.”

According to a study that appears in the May 2005 issue of the American Journal of Clinical Nutrition, most of us can eat all the carbs we want – just so long as they’re slow. And the slower the better.

Slow vs. low

I’ve actually covered slow-carbs in previous e-Alerts, but without the catchy name. A slow-carb diet is essentially a diet that restricts carbohydrates that rate a high glycemic index (GI).

A quick review: Low GI foods (such as meat and most fruits and vegetables) prompt a slow increase in blood sugar levels, while high GI foods (such as foods with added sugar, processed baked goods and starchy foods) produce a quick spike in blood sugar levels. A steady intake of high GI foods promotes a gradual insensitivity to insulin – the precursor of type 2 diabetes.

Researchers at Children’s Hospital in Boston designed a study to test the effectiveness of a slow-carb, low-GI diet using two key measures: weight loss and cardiovascular disease risk.

Twenty-three obese subjects were divided into two groups. One group of 12 subjects followed a conventional low-fat, reduced calorie diet. The other group of 11 subjects followed a low-GI diet, avoiding starchy foods and consuming protein along with any carbohydrates they ate. In addition, subjects in the low-GI group were unrestricted in their calorie intake. They were allowed to eat their fill and snack between meals. Subjects in both groups were urged to exercise regularly, and they all received counseling to help them stick to their diet and exercise regimens.

After one year the results were dramatic: Low-fat diet subjects lost just over six percent of their body weight on average, while low-GI diet subjects lost an average of nearly eight percent of their body weight.

In addition, one of the key markers for heart disease was much improved by the low-GI diet. Low-fat dieters reduced their triglyceride levels by less than 20 percent on average. Subjects on the low-GI diet, however, reduced triglycerides by nearly 40 percent. Another heart health marker provided an impressive result. Concentrations of plasminogen activator inhibitor 1 (a coagulation factor that increases blood clot risk) increased by more than 33 percent among the low-fat dieters, but DECREASED nearly 40 percent in the GI-diet group.

Keep it complex

In the e-Alert “So Five Minutes Ago” (2/23/04), I predicted that the buzz about low-carb diets would eventually evolve into popular recognition of the glycemic index as a logical dietary guide. I really wasn’t going too far out on a limb with that prediction. The glycemic index has been around for awhile, and it provides a convenient way to sort out simple carbs from complex carbs.

In a nutshell, simple carbs are fast (high GI), and complex carbs are slow (low GI). If your diet includes mostly complex carbs, you won’t put undue stress on your pancreas (the organ that uses insulin to remove sugar from the bloodstream). A high intake of simple carbs, on the other hand, prompts an over-secretion of insulin and, in time, a cycle of extreme blood sugar swings as the body desperately attempts to auto-regulate.

The problem is further complicated when the simple carbs come from refined sources (and they mostly do). Refining strips away natural fiber that slows the release of sugar into the system. HSI Panelist Allan Spreen, M.D., offers a more in depth look at the carbs issue in the e-Alert “Complex Made Simple” (6/23/04).

As for the glycemic index, there are several sources on the Internet that estimate the GI value of different foods. One in particular – – provides a complete GI database. The slight drawback for those of us in the U.S. is that the database is sometimes specific about brand names, which are mostly Australian and European (the site is maintained by the University of Sydney). Nevertheless, the database offers an excellent guide for making low GI dietary choices.

“Effects of an Ad Libitum Low-Glycemic Load Diet on Cardiovascular Disease Risk Factors in Obese Young Adults” American Journal of Clinical Nutrition, Vol. 81, No. 5, May 2005,