Ask a Dietitian

What’s the deal with Low Carb Diets?
Summary of the Current Issues on Low Carb Diets produced by the Dietitans of Canada. By Sinead Feeney, RD

Low Carbohydrate diets have been trialed by many hoping to lose some weight. This diet requires a person to lower their carbohydrate intake while increasing the percentage of protein that they consume instead. Some studies have been done to see what the short term and long term impact is on weight loss, and the effect on cardiovascular health and nutrient adequacy.

Short Term:
In the short term (under 6 months), studies found that low carb diets lead to greater weight loss than low fat diets (about 7 Kg versus 4 Kg respectively). However, this loss may have been due to better adherence to a low carb diet. Possible mechanisms for improved weight loss are: higher protein increases satiation (feeling of fullness), improves adherence and decreases the amount of refined carbs. However, other studies when comparing low and high carbohydrate diets found no difference in total weight loss and the weight loss pattern.

Long Term:
While the short term results appear more promising for this type of diet, the longer term results are not as positive. When people stayed on the diet for over a year, no difference was found for weight loss between low carb and high carb diets. In fact while people lost most of their weight in 6 months on a low carb diet, people continued to lose weight throughout the year on a high carb diet. It was found that in the long run, low carb was difficult to stick to and that adherence to a diet is the key predictor of weight loss success. In the end it is really the type of carbs and amount one is consuming that plays a major role in overall weight loss and maintenance.

Impact on Cardiovascular Health:
Some evidence showed a reduction in blood pressure, fasting serum insulin levels, C-Reactive protein and improved insulin sensitivity. As for cholesterol the studies were mixed, showing some improvement and in others an increase. Some studies also found that some following an Atkins diet showed an increase of 10% in their LDL cholesterol (a negative impact on the heart). All in all it was the weight loss rather then the diet that improved cardiac risk factors in some patients, not necessarily the diet itself.

Nutrition Adequacy:
For the most part those consuming less carbohydrate resulted in a decrease in nutrients including fiber, potassium, iron, magnesium, vitamin C, D, B6, Thiamin, calcium, sodium, riboflavin, in comparison to the baseline. Many of these nutrients are required for energy production. It was also found that people were consuming much more cholesterol due to the increase in animal fats.

My Suggestion:
Find a plan that is similar to what you like to eat.
Ensure it includes all 4 food groups and recommends regular activity
Set time aside to plan meals and do food preparation
Write a grocery list and shop once a week
Cook at home more, eat with the family or friends
Stay positive

The Bottom Line: The body requires carbohydrate for energy. In fact the brain relies completely on carbs for fuel. While eating a lot of refined carbohydrates can increase weight, eating whole grain products and other carbs such as vegetables and fruits that contain lots of fiber, is a very important part of a healthy diet. Diet and lifestyle changes should be sustainable for long term weight loss, health and overall enjoyment from your food. When you limit or restrict entire food groups, you lose out on a wealth of important nutrients for the body. So eat a balance and aim for ½ a plate of fruits and vegetables each meal, and a ¼ each for starch and protein.