Some swear by it to shed pounds and others call it a fad. What does the evidence show? Let’s take a deep dive into the science to find out whether a low carb diet is the answer for your weight loss goals.
Carbohydrates, fats, and proteins are the three basic nutrients we need daily to keep our body functioning properly. Carbohydrates, or “carbs,” are the starches, fiber, and sugars found in our foods that provide our body with its main source of energy. When we eat, our body converts our food’s carbs into the sugar glucose, which travels into the body’s cells where it can be used for energy with the help of insulin.
The reasoning behind a low carb diet
The rationale behind the low carb diet hinges on the workings of insulin. Carbohydrate foods that are high in starch or sugar are metabolized much more rapidly into glucose. This quick rise in glucose triggers the production of insulin, a hormone which also promotes the storage of fat. So the idea is that if we avoid the spike of insulin brought on by eating too many carbs, we can also avoid gaining weight. Followers claim that when we limit our carbs, we will fill our plates with more fats and proteins. These foods keep us full for longer and prevent dips in blood sugar, suppressing our appetite and overall calorie intake.
There is evidence linking losing weight with less carbs
Many studies have set out to determine whether reducing carbs can in fact lead to weight loss, and by and large, the evidence is pretty clear: low carb diets are as effective for weight loss, if not more effective, than other diets. Three such studies reflect the greater weight loss achieved with a low carb diet compared with a low fat diet:
Study 1: Obese subjects, 6 months
Study 2: Overweight subjects, 6 months
Study 3: Obese subjects, 2 months/22 months
Fewer carbs can also regulate blood sugar
Controlling carbs has been the cornerstone of diabetes treatment, and research validates why. In two studies where overweight or obese subjects with diabetes limited their carb intake, insulin sensitivity, A1c, and fasting blood glucose all improved compared with eating a low fat or low calorie diet:
Study 1: Obese subjects with diabetes, 6 months
Study 2: Overweight/obese subjects with diabetes, 6 months
Should you consider a low carb diet?
Before you toss out half your cupboard and hop on the low carb bandwagon, there are some key factors you should bear in mind first:
Þ Consider the subjects. The evidence linking low carbs with weight loss certainly seems convincing, but most studies included subjects who were obese or were obese and had diabetes. The jury is still out for those who do not fall into these categories.
Þ “Low carb” is subjective. Among low carb studies, carbs were restricted in all different quantities. Some considered 20 g to be low, while others capped carbs off at 30 g. As of now, there is no clear consensus on what defines a low carb diet.
Þ Long term effects are not known. Safety of a low carb diet is unknown long term because most studies only lasted a few months, and just a few spanned one to two years. Also, more research is needed to figure out how low carb, high protein diets rich in animal fats and unhealthy oils may affect heart and kidney health in the long run.
Þ Not all carbs are the same. In a low carb diet, healthy whole food complex carbs like vegetables, fruits, legumes, and whole grains are lumped together with unhealthy simple processed carbs like white bread, desserts, and sugary drinks. When healthy carbs are restricted, you miss out on the powerful fiber and antioxidants they offer.
Þ Weight loss may not last long. Greater weight loss may occur after six months on a low carb diet compared to a low-fat diet but results between the diets are generally the same after a year. Why? Sticking to any restrictive diet is a challenge, and most people eventually abandon their diets and gain back the weight.
Þ Your lifestyle is what matters. At the end of the day, what really matters most when it comes to losing weight and overall health is the lifestyle you lead, which includes regular exercise and eating in moderation. The total number of calories you take in and burn off ultimately determines whether you lose weight in the long run.