The Science-Backed Diet That a Longevity Expert Says Can Beat Weight-Loss Drugs

A leading scientist says a special eating plan can help people lose weight just as well as popular weight-loss drugs — and it may be safer in the long run. Professor Valter Longo runs the Longevity Institute at the University of Southern California. He believes most people should skip weight-loss drugs and instead eat foods that naturally help the body control hunger. His plan, called The Longevity Diet, focuses on eating more food, not less, while making smart choices about what goes on your plate.

Many weight-loss drugs work by copying a hormone called GLP-1, which stands for glucagon-like peptide-1. The gut releases this hormone after you eat, and it tells your brain that you are full and reduces cravings. These drugs do help people lose weight in the short term, but there are downsides. Side effects like muscle loss have been reported, and most studies show that people gain the weight back quickly once they stop taking the drugs.

Professor Longo says the better solution is to eat foods that cause the body to make its own GLP-1 naturally. When you eat large amounts of the right foods, your stomach and intestines feel full, and your body releases more GLP-1 on its own. This means you feel less hungry without needing any medication. 'In a world of Ozempic, what you want is a diet that makes your own GLP-1, instead of having to take pills,' he says.

One common mistake people make is simply eating fewer calories. Professor Longo says this approach often backfires. 'After a while, your body starts to worry because there are too few calories coming in, so it switches into energy-saving mode,' he explains. This means your body holds on to fat instead of burning it, and eating too little can sometimes cause you to gain more weight, not less.

The Longevity Diet is built around plant-based foods, with some fish and very little meat. Beans, whole grains, nuts, and seeds are the main sources of protein in this plan. The amount of protein recommended is lower than many modern diets suggest — about 0.37 grams per pound of body weight each day. This level provides just the right amount of an important building block called methionine, since too much can speed up aging while too little can make your body weak.

Research on mice showed that this type of diet raised GLP-1 levels while avoiding the muscle loss that often comes with weight-loss drugs. All eating should happen within a 12-hour window each day, such as between 8 a.m. and 8 p.m. Whole grains, fruits, and vegetables should make up most of the meals. Saturated fats — the kind found in fatty meats and some dairy products — should be kept to a minimum.

Professor Longo gives a clear example of what a good meal looks like on this plan. 'An ideal meal would be to have 250g of vegetables, 250g of legumes, then maybe some starches — 70g of rice or pasta,' he says. 'That's half a kilogramme of food. That's a big meal.' The key idea is that the food fills you up with nutrients, not empty calories.

The diet should also be personal, based on where you come from and what your ancestors ate. Professor Longo says people in the United Kingdom don't need to follow a Mediterranean diet — they should look at what their grandparents ate instead. For example, someone in the UK might swap pasta for potatoes, or use more fish and whole grains rather than legumes. The goal is to find a healthy pattern that fits your own background and food culture.

This eating plan may also slow down aging and help prevent some diseases. It can lower levels of a hormone called IGF-1 and raise levels of a protein called FGF-21, which together can help control blood sugar, reduce body fat, and even lower cancer risk. Professor Longo believes that doctors should start using diet as a form of medicine rather than jumping straight to drugs or surgery. He calls this kind of care 'real longevity medicine.'

Professor Longo does say that weight-loss drugs can be helpful in a few specific cases, such as for people who are obese or diabetic and have already tried healthy diets for years without success. But he is concerned that many people are using the drugs just to lose a small amount of weight when simple diet changes would work just as well. 'Weight loss drug's big mistake is trying to reach the end goal too fast, and that comes with lots of problems,' he says. His bigger message is that a diet you can stick with for life will always be more powerful than a drug you have to take forever.