Low Carb or Low Fat?

By: Isabel Smith, MS, RD, CDN

A recent study published earlier this month has spurred a lot of talk about low carb diets. Let’s take a look at the findings and find out what it means for you.

About the Study

  • The study was a randomized parallel group trial, which means that the participants did not know which of the two diets (low fat vs. lowcarb) they were assigned to (this method is the gold standard).
  • Included 148 men and women without diagnosed cardiovascular disease or diabetes (two factors which could have affected the outcomes).
  • Data regarding weight, cardiovascular risk factors, and dietary composition were collected at the beginning of the trial, again at 3, 6, and 12 months.

The Diets

  • One group was assigned a low carbohydrate diet that included less than 40 grams per day (equal to about 2 small apples for the entire day based on a 2,000 calorie diet).
  • The other group was assigned to a low fat diet comprised of <30% of total calories from fat daily with 7% or less total calories from saturated fat (that’s equal to about 34 grams of total fat including no more than 15 grams saturated fat, based on a 2,000 calorie diet).
  • Both groups received dietary counseling at regular intervals throughout the trial.

The Findings

  • At 12 months, the study participants in the low carbohydrate group lost on average 7.7 pounds more than those in the low fat group.
  • The results also suggest that participants in the low carbohydrate group (over the low fat group) experienced significant decrease in total fat mass, triglycerides, and in ratio of total high-density lipoprotein (HDL- the “good” cholesterol).

So what do these findings this mean for you?
This study sheds some light on the importance of healthy fats both for heart health and for weight loss and maintenance. Often dieters will try to cut back on fat (and even healthy fats) due to the notion that high-fat foods are “fattening.”

Well, I have news for you! Anything in excess can be fattening (even carrots!); foods that contain healthy fat are satiating and can help to promote feeling fuller for longer, which is essential for helping to promote portion control for weight loss.

Although this study may suggest that saturated fat isn’t quite as bad for us as we have once thought (given that the low carb group had unrestricted fat and may have included foods with higher saturated fat), I’d rather focus on recommending healthy fats and oils over saturated fat-containing foods like butter. Lastly, a major plus on the higher fat, lower carbohydrate diet was the benefit to blood lipids and improvement of triglycerides.

Tips for choosing fats:

  • Nuts and nut butters such as almond, cashew, macadamia and any other nut-butter you enjoy are a good choice.
  • Choose to use healthy oils such as olive, avocado, macadamia and flaxseed.
  • Choose plant-based foods with healthy fats such as avocado and coconuts.

Though the findings of this study lean more favorably in the direction of low carbohydrate intake for weight loss, it’s important to put into perspective how few carbohydrates the study included — about 2 apples per day total. It’s also important to discuss the potentially negative side effects of so few carbohydrates, including inadequate fiber and a huge reduction on total phytonutrients daily (because most fiber and phytonutrients come from plants that are mostly comprised of carbohydrates).

These points are important given that research has suggested that diets high in fiber (25+ grams per day) have been associated with reduced risk of colon cancer and diverticulitis. Additionally, research has also suggested positive benefit from antioxidants and anti-inflammatory properties found in colorful plant-based foods. That said, there is nothing wrong with limiting intake of grains, refined carbohydrates and certainly processed carbohydrates.

Shifting the diet to get all or most of your daily carbohydrates from plant-based foods such as fruits and vegetables (mostly vegetables) and a small amount of grains may be a positive way to reduce carbohydrate intake that may also help to promote healthful waistline.

Tips for choosing carbohydrates:

  • Choose carbohydrates rich in color (think nutrients) and high in fiber such as leafy and non-starchy vegetables of all colors and starchy vegetables in moderation (such as potatoes).
  • Choose carbohydrates that are unprocessed like quinoa, teff, buckwheat and brown rice over breads and refined grains.


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Isabel Smith, MS, RD, CDN

Isabel is a Registered Dietitian, wellness expert and fitness coach. Isabel has her own nutrition and wellness practice based in New York City, Isabel Smith Nutrition, but she works with clients and corporations both nationwide and worldwide in a variety of areas including skin health, weight loss, gastrointestinal issues and allergies, sports nutrition, general wellness and more. As a Guided Reboot coach, Isabel has helped hundreds juice their way to better health. When she isn’t helping clients achieve optimal nutrition and wellness, she can be found trying and creating new juices and making other healthy recipes, running, cooking, spinning, practicing yoga, and enjoying time with her two Yorkshire terriers. Isabel is also one of the nutritionists who runs our Guided Reboot programs.

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