The latest study, published July 11 in the Lancet Diabetes & Endocrinology, suggests that cutting just 300 calories a day, while maintaining an otherwise healthy diet, can significantly improve cholesterol, blood pressure and blood sugar levels, potentially reducing the risk of developing chronic diseases like diabetes and heart disease in the future.
The study was small but rigorous. Researchers asked 218 healthy, non-obese adults ages 21 to 50 to go through a range of medical tests. At the beginning of the study, most people were eating around 2,400 calories per day, according to self-reported food logs.
After baseline testing, almost 150 participants were for a month put on a regimented diet that reduced their normal calorie intake by 25%, while the rest acted as a control group. People in the diet group ate three meals per day at a study center and received nutrition counseling, while people in the control group continued their normal diets and did not receive any counseling. After the first month, the groups were told to maintain these eating patterns on their own for two years, while undergoing periodic health testing.
People in the calorie-restriction group didn’t follow directions perfectly—only 82% of them completed the full study and, on average, they maintained a calorie reduction of about 12% over the two years, rather than 25%. But the researchers found that even that drop, which translated to about 200-300 fewer calories per day compared to baseline, was associated with “persistent and significant” improvements in cholesterol, blood pressure, blood sugar markers and overall metabolic health, all of which are associated with a lower risk of chronic disease. Individuals in the control group didn’t see the same benefits.
Participants in the diet group also lost about 10% of their body weight on average. But the authors write that the cardiometabolic improvements observed in the study were “over and above” what could be expected from that amount of weight loss, suggesting there’s something uniquely beneficial about modest calorie restriction.
There’s a growing movement to shift away from calorie counting as a measure of health, and instead focus on the overall quality of the diet. One recent study, for example, showed that highly processed meals can affect the body differently than unprocessed meals with a nearly identical nutrient profile, which points to the difficulty of assessing a diet based on numbers alone. There are likely also mental health and lifestyle benefits associated with so-called “intuitive eating,” versus rigid calorie counting.
But at the same time, quite a few studies suggest that calorie moderation may be associated with health benefits beyond weight loss. A 2016 study, for example, found that slashing calories was associated with improvements in mood, sexual function and overall health. Studies in rhesus monkeys have found links between calorie restriction and longevity, and intermittent fasting—alternating calorie restriction with normal eating—has been linked to improved weight loss and lower chronic disease risk.
Extreme calorie restriction is dangerous, and any substantive dietary change should be discussed with an expert. But for most people, it’s relatively easy to cut 200 or 300 calories per day without a drastic change, or any obsessive monitoring.
Federal data also shows that snacks make up almost a quarter of the calories consumed by Americans each day. Since snack foods tend to be processed and packed with additives like salt and sugar, eliminating or improving the quality of snacks is a good target for a modest calorie reduction.