Researchers evaluated data for 37,233 adults gathered in the US National Health and Nutrition Examination Survey from 1999 to 2014. They divided participants based on the percentage of energy they got from fat, protein, and carbs, and they also noted if the respondents were eating a healthy or unhealthy version of that diet by evaluating the quality of carbs and fats. This means there were 4 different groups – unhealthy low-fat, unhealthy low-carb, healthy low-fat, and healthy low-carb.
For example, low-quality carbs included high-sugar foods and refined grains, while high-quality carbs included whole grains, non-starchy vegetables, and whole fruits. High-quality fats included foods high in unsaturated fat and low in saturated fat.
Quality of food matters more than diet type
The results of this low-carb vs. low-fat study showed increased total mortality for both unhealthy low-carb and unhealthy low-fat. Both of these dietary patterns showed very similar negative outcomes. Conversely, both healthy low-fat and healthy low-carb showed reduced total mortality.
“Despite variance in macronutrient composition, low-carbohydrate and low-fat diets have shown similar associations with weight loss and metabolic biomarkers, with similar intensity of energy restriction and adherence to the intervention,” the researchers wrote.
What’s the issue with unhealthy low-carb?
People on a low carb diet reduce their carbohydrate intake and increase their fat intake. That’s why the biggest risk on this diet lies in what sources of fat they choose in their diet.
“A high-saturated-fat diet is highly palatable and may have a weak effect on satiation, potentially leading to overconsumption and obesity,” the researchers wrote. This might explain why an unhealthy pattern of low-carb eating has such bad outcomes. The study suggests that replacement of saturated fats with unsaturated fats is associated with a lower risk of heart disease and mortality.
What’s the issue with unhealthy low-fat?
Low fat dieters eat a reduced amount of fat but an increased amount of carbohydrates. That’s why the quality of carbs is much more important to them.
“Low-quality carbohydrates, such as refined grains and added sugars, provide limited nutritional value, and their high glycaemic load could be associated with high postprandial glucose and insulin, inflammation, insulin resistance, and dyslipidemia,” the researchers wrote. This shows that simply going low-fat is not the solution either. Only when people choose high-quality carbs, such as whole grains, fruits, and vegetables, are they seeing better outcomes.
Focus on the quality of your food rather than macros
The message of this study is loud and clear. You will be better served if you focus on eating whole and quality foods instead of trying to hit a specific macronutrient ratio. That doesn’t mean going low-carb or low-fat won’t work for you. But it suggests that the type of carbs and fats you end up eating will have a significant influence on how well you do in terms of weight loss and your overall long-term health.