In an intriguing study conducted by the National Institutes of Health, researchers have unearthed some surprising facts about diet and health.
The study, led by the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) and published in Nature Medicine, compared two diets: a low-fat, plant-based diet and a low-carbohydrate, animal-based diet.
The aim was to understand how these diets impact calorie intake, hormone levels, body weight, and overall health.
Kevin Hall, Ph.D., a Senior Investigator at NIDDK, led the research. The study was motivated by a need to understand whether high-carb or high-fat diets lead to greater calorie intake.
Twenty adults, including 11 men and nine women, participated in the study, none of whom had diabetes. They spent four continuous weeks at the NIH Clinical Center’s Metabolic Clinical Research Unit, following each diet for two weeks consecutively.
Both diets consisted of minimally processed foods and had equal amounts of non-starchy vegetables. The low-fat diet was high in carbohydrates, while the low-carb diet was high in fats. Participants had access to three meals a day plus snacks and could eat as much as they wanted.
The results were surprising. On the low-fat diet, people consumed 550 to 700 fewer calories daily than on the low-carb diet.
Despite this difference in calorie intake, participants reported no differences in hunger, enjoyment of meals, or feelings of fullness between the two diets.
Interestingly, while both diets led to weight loss, only the low-fat diet resulted in a significant loss of body fat.
Hall pointed out that even though the plant-based, low-fat diet included foods that caused noticeable fluctuations in blood glucose and insulin, it did not lead to overeating, challenging the assumption that high-carb diets always cause people to eat more.
Conversely, the animal-based, low-carb diet didn’t result in weight gain despite being high in fat.
This study suggests that the factors leading to overeating and weight gain are more complex than just the amount of carbs or fat in the diet.
For example, Hall’s previous research indicated that ultra-processed foods lead to overeating compared to minimally processed foods, regardless of their carb and fat content.
The plant-based, low-fat diet in the study comprised roughly 10.3% fat and 75.2% carbohydrates, while the animal-based, low-carb diet consisted of 10% carbohydrates and 75.8% fat. Both diets included about 14% protein.
For dinner, a low-fat meal might include a baked sweet potato, chickpeas, broccoli, and oranges, while a low-carb meal might feature beef stir fry with cauliflower rice. Participants were free to choose their portions.
Hall noted that both diets showed benefits in the short term.
The low-fat, plant-based diet curbed appetite, while the animal-based, low-carb diet led to steadier insulin and glucose levels. However, it’s still unclear if these differences would persist over the long term.
The study wasn’t designed to recommend diets for weight loss, and the findings might differ in a non-clinical setting, where factors like food costs and availability can affect diet adherence.
The controlled environment ensured accurate data but might be hard to replicate in everyday life.
NIDDK Director Griffin P. Rodgers, M.D., emphasized the importance of rigorous science in achieving good nutrition, especially during challenging times like the COVID-19 pandemic.
This study takes a step forward in answering questions about how our diet choices impact our health.
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The research findings can be found in Nature Medicine.
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