Calorie Quality vs. Quantity: What Matters Most?

Diet advice is often given when trying to lose weight, with suggestions ranging from cutting carbs to limiting fat. Professor Christopher Gardner, PhD, from Stanford University, conducted research to determine the effectiveness of different approaches.

Research published in JAMA compared low-carb and low-fat diets for weight loss. The study followed 609 overweight adults for a year and found that both groups lost similar amounts of weight: 11.7 pounds for those on a low-fat diet and 13.2 pounds for those on a low-carb diet.

“There isn’t one diet for everyone.”

Within the groups, there was significant variation in individual weight loss. Some participants lost up to 60 pounds, while others gained weight. This led Gardner to conclude that “There isn’t one diet for everyone.”

While prescribing a specific diet may not be universally effective for weight loss, the research provided valuable insights.

Participants were not required to consume a specific calorie count, but all were instructed to reduce either fat or carbohydrate intake (depending on their assigned group), opt for more whole foods, including vegetables, and minimize added sugars and refined grains. Those adhering to this advice, prioritizing the quality over the quantity of calories consumed, experienced substantial weight loss—regardless of whether their diets were low-carb or low-fat.

“Steel-cut oats and kale both fall into the low-fat category; so do sodas and white bread, yet oats and kale are likely more filling, more satiating. Avocados and nuts are both low-carb; so are lard and butter, but meals incorporating avocados and nuts might be more filling, more satiating,” Gardner clarifies.

Focusing on healthier, more satiating foods aided dieters in feeling full while consuming less.

An earlier JAMA study, published in 2012, reported similar findings. Twenty-one overweight adults were assigned to follow one of three diets: low-fat, low-carb or low-glycemic index for a period of four weeks. Participants were instructed to replace grains and starches with vegetables, legumes, fruits and healthy fats. All dieters lost weight, but those who opted for fewer carbs and consumed more high-quality calories also experienced an acceleration in their metabolisms, burning an additional 325 calories per day—roughly equivalent to the number of calories burned during an hour of moderate-intensity physical activity.

“The quality of the foods we consume can exert fundamental effects on hormones, metabolism and even the expression of genes throughout the body.”

The type of calories we eat impacts how many calories our body burns. Dr. David S. Ludwig, co-director of the New Balance Foundation Obesity Prevention Center at Boston Children’s Hospital, explains that from a metabolic standpoint, all calories are not equal to the body. “The quality of the foods we eat can have fundamental effects on hormones, metabolism and even the expression of genes throughout the body.

While the number of calories consumed still matters, Gardner believes it's more important to choose foods that make you feel full and satisfied rather than fixating on a specific calorie count.

So, yes, losing weight involves eating fewer calories, but it's not as simple as just eating less. We should consider these quality components to be foundational to any kind of diet or eating pattern, whether it's low-fat, low-carb, paleo, vegan, Mediterranean, or another diet. The key is to find combinations of low-fat or low-carb meals and menus that you enjoy and could sustain over time to support your weight goals.