Brunal is a Ph.D. candidate in the Translational Biology Medicine and Health graduate program at the Fralin Biomedical Research Institute at Virginia Tech.

Over the last 30 years, the number of Americans considered obese has grown vastly. Between 2015 and 2016, ~39% of adults in the United States were considered to be obese. Two questions surround this portion of the U.S. population: Why is this happening, and what can we do about it? New research conducted by Dr. Keven D. Hall’s group at the National Institute of Diabetes and Digestive and Kidney Diseases may provide some insight. His lab is interested in the relationship between calorie intake and calorie output. Standard nutritional dogma states: if you decrease the number of calories in and maintain the number of calories out (create a caloric deficit) you should lose weight. Dr. Hall’s group challenged that by asking: Does the rate and type of weight loss depend solely on the calorie deficit or does where your calories come from play a role? Many of U.S. have heard of many fad diets: Keto, Paleo, low-fat, low-carb, intermittent fasting, etc. Dr. Hall’s group investigated the differences between these low-fat and low-carb diets. They found, when given the same number of total calories, there was no difference in weight loss and no change in fat loss between these diets. To further investigate this finding, they performed a meta-analysis, taking data from many previous studies, to see if there were any significant differences between low-fat and low-carb diets. They found no difference in metabolic rate and no difference in fat loss.

So, there appear to be no significant differences between low-fat and low-carb diets. But what about other diet choices like plant-based vers U.S. animal-based, or processed vers U.S. unprocessed foods? There has to be something in people’s diets that has changed where some people gain weight while others don’t, right?

Unprocessed foods are raw untouched parts of plants and animals such as raw meat and leafy greens that don’t have added sugars or preservatives and have a large amount of nutrients. Processed foods, on the other hand, have been manipulated in some way, often with the addition of artificial sugars, preservatives, artificial dyes, etc. and have fewer nutrients and are usually high in calories. In recent times, we have seen a sharp increase in the number and availability of processed foods. Specifically, we have seen an increase in the availability of Ultra-processed foods, which have little to no resemblance to their unprocessed parent products and have little to no nutritional value. Some examples of Ultra-processed foods that we’ve seen increase include processed grains (such as bread, cakes, pastries, candy, sugary sodas, etc). Because of this increase, Dr. Hall’s lab most recently went on to answer the question: Is there a difference between ultra-processed and unprocessed foods? They performed a study, where they provided participants a diet consisting of mostly processed food or a diet of mostly unprocessed food. The same number of calories were made available (double what they would require for a typical day) and they were allowed to eat as much or as little as they wanted. What they found was striking: Those that were given processed foods gained weight and consumed nearly 500 MORE calories per day than the unprocessed group while those that were given the unprocessed foods lost weight on average. So, this means SOMETHING about processed foods causes people to eat more, leading to weight gain. Here is the big question: Why? While we don’t fully know the answer yet, highly processed foods are less dense and less filling but have more calories. This means anyone will eat more calories before feeling full. For example, because broccoli is less calorie-dense than a donut, you will feel full sooner, all while still consuming fewer calories.

Research has demonstrated that obesity is associated with increased risk of diseases such as heart disease and diabetes. With heart disease being a major killer of Americans, it is important to find new ways of examining the obesity epidemic in this country. We still have a way to go, and eating healthier isn’t easy. Many people find healthier food to be less palatable (less tasty) at first, which can make it difficult to stick to a new diet plan. Perhaps including more of what our ancestors ate, preparing food at home, using fresh fruits and vegetables, and limiting our consumption of processed foods and meats, might at least lead U.S. in the right direction.