A Harvard University obesity medicine expert pinpoints one type of food to eliminate to achieve this possible life-lengthening result.
For those of us who grew up in a generation that emphasized thinness, more modern perspectives are welcome, such as from Fatima Cody Stanford, MD, MPH, MPA, an obesity medicine expert at Harvard who suggests calorie-counting is not the way: “Drop the calories notion,” Dr. Stanford says—and instead focus on high-nutrient foods that support a healthy gut, while also managing stress, sleep, and exercise.
It sounds appealingly simple, right? Well, new science shows there may still be some utility to counting calories. That’s according to an October 2025 study by longevity and biochemistry researchers at a national university in Taiwan. In the Journal of Biomedical Science, the study highlights that different forms of dietary restriction—including cutting calories, intermittent fasting, and time-restricted eating—can offer benefits beyond weight loss. The researchers concluded that when combined with good nutrition, these strategies can help improve metabolism, extend quality of life, and even lengthen lifespan.
One approach in particular—cutting daily calories by about 25%—was reported to improve several key markers of health, as long as nutritional needs are still being met.
Pointing to the well-known CALERIE study (Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy), a two-year randomized controlled trial that looked at calorie reduction in non-obese individuals, the researchers noted that moderate calorie restriction led to meaningful improvements in aging-related biomarkers like:
- insulin sensitivity
- blood pressure
- inflammation
- cholesterol levels
- Participants also showed better muscle function and a stronger immune system, suggesting that calorie reduction can support tissue health as we age.
The researchers noted that past non-human studies involving yeast, fruit flies, rodents, and more have identified similar benefits, some cutting calorie consumption by 30% to 40%. In rhesus monkeys—genetically and physiologically one of the most similar to humans—calorie restriction reduced incidence of cancer, cardiovascular diseases, and metabolic disorders while helping to preserve brain volume and enhance cognitive function.
How exactly does calorie restriction support healthy aging? Many mechanisms appear to be at play, but one key way is that it boosts what’s known as “metabolic flexibility”—the body’s ability to shift from burning mostly glucose to using other fuel sources when needed. A separate 2022 study on metabolic health stated: “Our modern lifestyle often leads to chronic overnutrition, where the body constantly takes in a mix of fuels.”
If the body can’t efficiently process this fuel mix, it may lead to problems like damaged proteins, cell injury, and eventually disease, that study noted. This concept may also help explain why intermittent fasting has been shown to reduce chronic disease risk in some cases.
The researchers in the 2025 study emphasize that the goal is to reduce caloric intake without missing out on the foods your body needs to thrive. For what’s considered the standard, 2,000-calorie American diet, Harvard’s Dr. Stanford says one simple way to cut 500 calories is to get super intentional about cutting out one type of food. In a study that investigated weight changes between two groups, one eating processed food and the other eating all-natural, “People who ate the ultra-processed food gained weight,” Dr. Stanford said. Harvard Medical School adds that the processed food-eater consumed “500 calories more each day on average. The same people’s calorie intake decreased when they ate the unprocessed foods.”
For daily wellness updates, subscribe to The Healthy by Reader’s Digest newsletter and follow The Healthy on Facebook and Instagram. Keep reading:
- 5 Benefits of Wearing a Continuous Glucose Monitor if You Don’t Have Diabetes, According to Expert Dietitians
- Dieting? A New Study Found Fasting at This Hour Was More Powerful for Blood Sugar and Weight Loss Than Cutting Calories
- Intermittent Fasting and Heart Attacks: Doctors Address the Link
- Microbiologists: Eating This Regularly Protects the Gut from “Inflammation-Related Damage”
