Evidence that Low Carb Diets are Safe and Effective

Claims are sometimes made that “low carb diets are a fad” and “there needs to be scientific evidence to demonstrate they are both safe and effective“. What is the evidence?

In fact, a low carbohydrate diet is not new and was the standard recommendation for treating Diabetes prior to the discovery of insulin. More than 150 years ago, the first weight-loss diet book (ironically written by William Banting, a distant relative of Sir Frederick Banting, the co-discoverer of insulin) focused on the limiting the intake of carbohydrates, especially those of a starchy or sugary nature. The book was titled Letter on Corpulence – Addressed to the Public (1864) and summarized the advice of the author’s physician, Dr. William Harvey that had enabled Banting to shed his ‘portly stature’.

Recent 10 week results of a nonrandomized, parallel arm, outpatient intervention using a very low carb diet which induced nutritional ketosis  was so effective at improving blood sugar control in Type 2 Diabetes, that at the end of six months >75% of people had HbA1c that was no longer in the Diabetic range (6.5%). Details of the findings from this study titled A Novel Intervention Including Individualized Nutritional Recommendations Reduces Hemoglobin A1c Level, Medication Use, and Weight in Type 2 Diabetes are available here.

I recently reviewed 2 two-year studies that demonstrated that low carb diets are both safe and effective for weight loss and improving metabolic markers;

  1. This long-term study titled Weight Loss with a Low-Carbohydrate, Mediterranean, or Low-Fat Diet clearly demonstrated that a low carb non–calorie-restricted diet was both safe and effective and produced the greatest weight loss, lower FBS and HbA1C, the most significantly lower TG and higher HDL and lower C-reactive protein (when compared with a  low-fat calorie-restricted diet and a Mediterranean calorie-restricted diet).
  2. This 2-year, randomized control study of more than 300 participants  titled Low Fat Calorie Restricted Diet versus Low Carbohydrate Diet – a two year study found that both diet groups achieved clinically significant and nearly identical weight loss (11% at 6 months and 7% at 24 months) and that people who ate the low-carbohydrate diet had greater 24-month increases in HDL-cholesterol concentrations than those who ate a low-fat calorie restricted diet. As well, a significant finding of this study was a very favourable lowering of LDL for the first 6 months and lowering of both TG and VLDL for the first year.

These long-term data provide evidence that a low-carbohydrate diet is both a safe and effective option for weight loss and that this style of eating has a prolonged, positive effect on metabolic markers.

But is this all the evidence we have?  By no means!

Below is a list of research studies and meta-analyses (complied by Dr. Sarah Hallberg) that used a low-carb intervention. These span 18 years, 76 publications, involve 6,786 subjects, and include 32 studies of 6 months or longer and 6 studies of 2 years or longer. At the bottom of this post is a downloadable pdf of this list. [Note: text in green represents meta-analyses.]

Hardly a passing fad!

Low carb diets have been well-studied and found to be both safe and effective.

Many thanks to Dr. Sarah Hallberg, a Physician and exercise physiologist from West Lafayette, Indiana (Twitter: @DrSarahHallberg) for compilation of this list.

A complete list of the Low Carb Diet studies to date (compiled by Dr. Sarah Hallberg) is available here.

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