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Low-Fat or Low-Carb? Neither! Healthy Is Best!

Natalie Stein
January 29, 2020
Low-Fat or Low-Carb? Neither! Healthy Is Best!

What is the best diet to follow?

Is a low-fat or low-carbohydrate diet better? Finally, we may have an answer, and it is great news. The answer is neither, or, to put it another way, whichever you prefer.

For years, experts urged the public to cut fat to lose weight and improve heart health. This often led not only to beneficial results such as trimming fat from meat, but also to harmful effects such as adding refined carbohydrates to the diet as a replacement for fat.

When the plethora of low-fat and fat-free products on the market did not curb the obesity epidemic, and researchers began to understand that some fats are healthier than others, opinions began to shift. Low-carb diets became popular, with bacon, steaks, butter, and eggs being among the most notorious components.

The debate has continued, but a recent study has shed some light on the low-carb versus low-fat debate. It turns out that the best diet is…a healthy one! Read on for what Harvard researchers found, how you can design your own best diet for lowering risk of mortality, and how Lark can help.

Harvard Study on Diet and Mortality


Researchers at Harvard decided to look at what people were eating and whether low-carbohydrate or low-fat diets led to a greater chance of mortality. They used data from the National Health and Nutrition Examination Survey (NHANES), which is an ongoing survey by the Centers for Disease Control and Prevention (CDC). 

Researchers included data from everyone who was over 20 years old, who had participated in NHANES between 1999-2014, and who had provided information on their diets. They categorized diets as low-fat or low-carb, and further broke those down into healthy or unhealthy low-fat or low-carb. Next, they looked for associations between diet type and mortality, or risk of death.

Results were published in JAMA Internal Medicine. It turns out that neither overall low-carb or low-fat diets were associated with higher or lower mortality rates. That is, it did not matter whether participants ate a low-carb or low-fat diet. What did matter, though, was whether the diet was healthy. Both healthy low-carb and healthy low-fat diets were linked to lower risk of death, and unhealthy low-carb and unhealthy low-fat diets were linked to higher mortality during the study.

Low-Fat and Low-Carb Diets Defined


Carbohydrates, protein, and fat are the nutrients in the diet that contribute the most calories. Low-fat diets tend to be high in carbohydrates, while low-carbohydrate diets tend to be high in fat and protein. 

  • Sources of carbohydrates include bread, cereal, pasta, and other grains and grain products, fruit, sugary foods and beverages, starchy vegetables, beans, and dairy products.
  • Sources of protein include meat, fish, poultry, eggs, dairy products, soy products, beans, nuts, and lentils.
  • Sources of fat include oils, avocados, butter, lard, shortening, fatty meats and poultry, seeds, nuts, and dairy products.

“Healthy” and “Unhealthy” Diets Defined


As you can gather from the above list of high-carb, high-protein, and high-fat foods, they can all range from healthy to unhealthy. Researchers in the Harvard study assigned foods and nutrients to “healthy” or “unhealthy” categories, then put them together to categorize each person’s diet according to its overall health.

No food is entirely healthy or unhealthy, but most foods are closer to one or the other. 

  • For carbohydrates, healthier ones are typically less processed, higher in fiber, and free from (or low in) added sugars. In the study, “high-quality” carbohydrates were whole grains, whole fruit, non-starchy vegetables, and legumes (beans, peas, soy, and lentils).
  • For protein, healthier ones tend to be low in saturated or total fat. In the study, researchers noted animal versus plant proteins.
  • For fats, healthier ones tend to be free from artificial trans fats and low in saturated fat compared to the amount of unsaturated fats, especially monounsaturated and omega-3 fats. In the study, researchers looked at the amounts of saturated fats and unsaturated fats.

This table can help guide choices.

How Much Difference Does a Healthy Diet Make?


This study included an average follow-up period of 8 years. Compared to a diet whose healthy quality was middle-of-the-road, those who followed the healthiest low-carb diets were less 27% less likely to die during the study period. The healthiest low-fat diets were linked to the exact same benefit: a 27% reduction in mortality!

Similarly, the least-healthy low-carb diets were linked to 16% higher risk of mortality, while the least-healthy low-fat diets were linked to a 12% greater risk. Deaths from cancer and heart disease both showed trends towards being less prevalent among the healthier eaters.

Following Your Own Longevity Diet


Without even being in a nationwide study, you can create your own diet to improve health and lower risk for mortality. As the results of this study suggest, there is plenty of room for customization in a longevity diet. Whether you love carbs or cannot imagine life without meat and cheese, there are ways to add health-promoting nutrients to, and subtract less-healthy components from, your everyday meals.

These are some general guidelines.

  • Add vegetables
  • Etc
  • Natural, whole, less processed
  • Add treats

Everyone’s diet is different, but these are some possible menus for “healthy low-carb,” “unhealthy low-carb,” “unhealthy low-fat,” and “unhealthy low-fat” menus so you can get an idea.

Lark offers personalized nutrition coaching to support a nutritious diet that works for you as an individual. Features include instant feedback after logging meals, tips and tricks for fitting good food into any kind of lifestyle, and reports on progress over recent weeks. You will never be alone with Lark in your pocket!

Written by Natalie Stein on January 29, 2020
Exercise, Fitness & Nutrition Expert | Lark Health
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