Eating vegetable soup can add years to your life. In fact, you might be smarter—and slimmer—if you take regular breaks from your usual routine and simply eat vegetable soup for a few days. This practice is called semi-fasting, and the potential health benefits are outlined in a recent study published in Cell Metabolism.


It’s all about cutting calories by half for just a few days—with a specific combination of proteins, carbohydrates, fats and micronutrients, explains Valter Longo, PhD, professor of biogerontology at the University of Southern California’s Leonard Davis School of Gerontology and director of the USC Longevity Institute.

His study of elderly mice showed that a four-day, low-calorie diet given every two weeks reduced cancer incidence and improved immunity. The mice also had less evidence of bone mineral density loss (so their bones were stronger than the control mice), less inflammation (a risk factor for many chronic diseases including cancer, cardiovascular disease, diabetes and high blood pressure) and better brain power (with improved learning and memory and evidence of new brain cells). The rats also lost weight, including belly fat. And they lived longer compared to rats that didn’t get the semi-fasting diet.

Next, Longo tried his theory on a small group of humans. Once a month for three months, 19 people followed Longo’s four-day semi-fasting diet, slashing caloric intake down to 34 to 54 percent and significantly cutting protein consumption. Dieters were restricted to vegetable soups, energy bars, energy drinks, chips, chamomile flower tea and a vegetable supplement tablet.

After the four-day diet, everyone went back to their normal eating habits, just as the mice did, eating anything they wanted. When their results were measured against a control group that had no special diet, the dieters’ blood tests showed less evidence of aging, diabetes, cardiovascular disease and cancer.

According to Longo, this diet works by decreasing the IGF-I hormone, which promotes aging and has been linked to cancer risk. His human dieters also had lower levels of IGFPB hormone and C-reactive protein (a marker for inflammation linked to heart disease), and less evidence of diabetes and trunk fat (belly bulge). Yet there was no loss of bone or muscle strength, which is always a concern with fasting diets.

In earlier studies, Longo proved that fasting can starve cancer cells yet protect immune and other cells from chemotherapy toxicity. “It’s about reprogramming the body so it enters a slower aging mode, but also rejuvenating it through stem cell-based regeneration,” he says. “It’s not a typical diet because it isn’t something you need to stay on.”

Unlike water-only fasting, which Longo believes is too severe and should only done in specialized clinics, this semi-fasting diet is safe for most healthy people. Anyone with a BMI of 18 or less and diabetics taking insulin or diabetes medications should not try this diet. And if you’re obese, you must consult with your doctor first, he adds. Everyone else should be able to follow this semi-fasting diet every three to six months for increased longevity and better health. 


  1. Cell Metabolism
  2. USC press release
  3. ScienceDaily