Which came first?  High carb diets or expanding waistlines?  Since the birth of the recommendation to reduce fat and increase carbohydrate in the American diet, the incidence of obesity has increased.  While much of this uptick in weight is linked to increased portions and total caloric intake, recent survey data suggests that individuals view carbs as the culprit with over a third of individuals voicing their belief that they should be eating fewer carbs.

As someone working with active individuals seeking better health, wellness, and performance, there’s a good chance that you’ve been asked about the value of going “low carb”.  As a sports RD, I get similar questions, typically posed by weight loss warriors, endurance athletes, and individuals with body composition goals.  So are carbs really the demon that they’ve been made out to be?  Is low carb the way to go if weight loss is needed?  Answer: It’s complicated.

Defining the Diet

There are many variations on what constitutes a “low carb diet”.  Technically, any intake that falls below the Acceptable Macronutrient Distribution Range (AMDR) is low carb.  The AMDR, established by the Institute of Medicine of The National Academies, provides research-backed guidance around intake of the commonly tracked macros – carbs, protein, and fat.  The AMDR for carbs is 45-65% of daily calories; an intake below 45% of calories from carb is technically “low carb”.  

What Does the Science Say?

Most individuals cutting carbs aim for an intake far below 45% of total calories and many lower carb interventions advocate for less than 25% of calories from carb.  Critics of these diets suggest these plans lead to poor long-term outcomes and even an increase in mortality, relying on epidemiological data to support their stance.  But for many, the efficacy outweighs the debatable risk and a recent study published in the BMJ found that people who followed a low-carb diet (20% of calories from carbs) burnt more calories (a shift of +50-70 calories/day for every 10 % reduction in carbs) compared to those who consumed a high-carb (60%) diet, thus offering a path for weight loss and a potential weapon to fight metabolic syndrome.  Another study examining the effects of a low-carb diet (<40g/d, macros at 34%C/24%P/41%F) compared to a low-fat diet (<30% of energy from fat, macros at 54%C/19%P/29%F) on weight loss and cardiovascular disease risk.  Over one year of eating similar energy intakes, the low carb group ended up losing almost 3x as much weight as the low-fat group and experienced more significant improvements in body composition and other risk factors.

Is Low Carb Right for Your Client?

Criticism of low carb plans echo criticisms of any diet; improperly designed plans lead to insufficient intake of certain vitamins and minerals and excessive intake of others, lack of variety, and poor adherence.  But proponents cite the potential for reductions in appetite, cardiovascular risk markers, fasting blood glucose and triglyceride levels, and weight loss as reasons to cut carbs.  But to succeed and stay the course, clients need to understand which foods fit and be willing to invest in meal prep, tracking, and the other tools that make this diet, and any diet, work.

Is Low Carb the Only Way?

The outcomes of following a well-designed low-carb diet are compelling.  Still, I’d be remiss if I didn’t mention that similar outcomes can follow other healthy ways of eating.  What’s most important is to find a way of eating that promotes health, wellness, and performance goals and fits lifestyle needs.  Another note, low-carb diets are not typically recommended for intense cardio junkies, athletes in heavy training, and those looking to hit a new PR.  While the extra protein in these plans is clutch for athletes needing this nutrient for recovery and repair, these plans result in a reduction in glycogen stores (i.e. muscle fuel).  This means less high-octane fuel in the tank so if the goal is to go fast and long, a low carb diet isn’t’ likely to get you there.     

Parting Thoughts

Think of low carb like you would any other piece of equipment you use in practice.  It’s not for everyone including but not limited to athletes in heavy training, individuals with certain chronic conditions, those with protein restrictions, and most pregnant women.  For all of us, however, we can’t go wrong with making more choiceful carb choices, reducing added sugar intake, and swapping refined grains for heart healthy fats and high quality proteins.