Feb. 28. 2018
Written By:
McKel (Hill) Kooienga
McKel Hill Kooienga, MS, RDN, LDN

McKel Hill Kooienga, MS, RDN, LDN

Founder of Nutrition Stripped and the Mindful Nutrition Method™

A big new study on low-fat vs. low-carb diets proves that the best diet is one you can stick to.

The nutrition and health world was abuzz last week with the emerging research findings of a year-long study that was published in JAMA by the American Medical Association. Both low-fat and low-carb diets had similar weight loss results over the course of a year.

About The Study

This year-long study, led by Dr. Christopher Gardner of Stanford University along with the US National Institutes of Health, the Nutrition Science Initiative, and additional groups led by nutrition experts, researched more than 600 participants in a randomized clinical trial on low-fat vs. low-carb diets.

Low-Fat Vs. Low-Carb: The Focus of the Study

Before now, reasons for individual responses on low-fat and low-carb diets have not been well understood. Why did some people have more success on one over the other? Was low-fat or low-carb better for weight loss? This question has fueled the diet industry for decades.

The low-carb model proposes a carbohydrate-insulin hypothesis, which suggests that a diet heavy in carbohydrates directly leads to weight gain. Refined grains and sugars, especially, have been believed to be the root of insulin spikes, stopping the body from burning calories and instead, holding onto fat.

Previous research led researchers to wonder if insulin sensitivity or genetics determined the success of dieting. This recent study aimed to test these two factors and the ability to predict weight loss — while on either a low-fat diet or low-carb diet. The study set out to test two things: a potential link between genetics and diet type for weight loss, and the link between insulin secretion and the diet type for weight loss.

The Participants

The participants’ average age was 40, plus or minus 7 years, and their average body mass index (BMI) was 33, which is considered class I obesity. Over the course of a full year, the participants were instructed to attend more than 20 dietary counseling sessions with a registered dietitian — and they weren’t all A+ students. The average attendance was actually 66% for both the low-fat group and the low-carb group.

No Calorie-Counting Here

The first two months of the study proved to be more restrictive than the rest of the year. During this stage, the low-fat group was instructed to eat only 20g of fat/day, while the low-carb group was instructed to only 20g of carbs/day.

If these levels sound low — they are. Both groups were not expected to stay at these levels for the entire course of the study, and they both started introducing more fat and carbs into their diets after the first two months. Each participant was instructed to reach their lowest sustainable level that they could maintain personally. By month 3, the low-fat group was averaging 42g of fat per day, and the low-carb group was averaging 96.6g of carbs per day, which was exponentially higher than the baseline level.

This study didn’t include calorie-counting; neither group was told a target number of calories to consume per day. Instead, both were encouraged to focus on whole foods and drinks. Instructions included minimizing food and drink with added sugars, refined flours, and trans fats. This emphasis on minimally processed and nutrient dense foods aligns with the NS Food Philosophy on nourishing food — and it echoes our sentiment about preparing foods at home as much as possible.

What Science Tells Us

This study and its findings definitely take a big swing at the popular low-carb model that has been believed and shared in recent decades. This emerging research tells us that carbs aren’t the magic piece of the weight and fat loss puzzle.

You won’t see significantly different weight loss results between low-fat or low-carb diets, even if you’re insulin sensitive.

According to the carbohydrate-insulin hypothesis, researchers expected to see body fat loss accelerate when the insulin secretion was cut by 50%. When this didn’t happen, it suggested that there are more factors at play with our insulin levels than the number of carbohydrates we eat.

The research into a low-fat vs. low-carb diet proves that one model isn’t better than the other. This study’s results shed more light on the relationship between genetics, insulin production, and diet intervention. We still can’t pin down a super-direct relationship, but we have a better understanding than we did before. It will be very interesting to stay tuned for further analysis and next steps after this monumental study.

Practical Takeaways From The Study

As part of the NS Food Philosophy, enjoy whole foods from the earth and limit processed foods that contain hydrogenated oils, and other preservatives that our bodies don’t need for optimal health. Granted, there are great convenient whole food products in a bag or wrapper, just check the ingredients and make sure you understand what’s truly in that food. Better yet, challenge yourself to make more recipes, meals, and snacks from home anchored in whole foods.

Scientific research has continually shown the many health benefits of eating a diet high in plant foods from the earth: fruits, vegetables, nuts, seeds, grains, legumes, and beans. Plant-based foods contain fiber to keep our microbiome healthy and balanced with good bacteria, phytonutrients, antioxidants, vitamins and minerals we need to thrive. We don’t need science to tell us how good eating plants makes us feel, try it for yourself and befriend these powerhouses of nutrition. Read more about

Here are a few practical takeaways to put into action from this study:

  • Focus on whole foods and vegetables
  • Prepare meals with whole-food ingredients at home
  • Limit processed foods
  • Minimize sugar, refined flour, and trans fat
  • Be wary of restrictive diets — instead, find a diet that works for you and is sustainable for your personal lifestyle


  1. Gardner CD, et al.. Effect of Low-Fat vs. Low-Carbohydrate Diet on 12-Month Weight Loss in Overweight Adults and the Association with Genotype Pattern or Insulin Secretion: The DIETFITS Randomized Clinical Trial . JAMA. (2018)

Additional Reads

  1. Low-fat vs low-carb? Major study concludes: it doesn’t matter for weight loss, Examine
  2. We’ve long blamed carbs for making us fat. What if that’s wrong? Vox

What Do You Think?

What are your thoughts on these latest findings? Have you been reading up on this emerging research, too? What are your questions on what this means for your health? Keep the conversation going by commenting below, or connecting with NS on Instagram.