In a world saturated with dietary fads and wellness trends, it’s easy to feel overwhelmed by conflicting advice. Every week, a new miracle diet emerges, promising to transform your health overnight. Yet, according to leading nutritionist Federica Amati, the secret to long-lasting health isn’t found in the latest superfood or a restrictive eating plan. Instead, it’s much simpler: you need to eat more fiber.

Amati, a respected nutritionist and medical scientist, has spent years researching how diet impacts everything from mental health to longevity. During an interview following the Hay Festival, she delivered a message that cuts through the noise of modern nutrition trends. Her advice is refreshingly straightforward: focus on fiber-rich foods like whole grains, legumes, and vegetables to significantly boost your health.

“Our grandmothers were right,” she said during an interview with ZME Science. “The simple things they told us, like eating your vegetables first, have always been good advice, and now science is backing it up.”

Science-Based Advice

“The majority of us, about 90% of adults in the UK and up to 95% in the US don’t get the minimum dietary requirement for fiber every day. So, we need about 30 grams of fiber per day, and we’re on average getting 18. We’re really far off the mark. So, start with that fiber first is a really good way to do it.”

This gap may not seem alarming at first glance, but the consequences of a fiber-deficient diet are far-reaching. Fiber, found in plant-based foods like vegetables, legumes, and whole grains, is essential for maintaining a healthy digestive system. It’s also linked to a lower risk of chronic diseases, including heart disease, diabetes, and certain types of cancer.

Amati highlights how fiber acts like a foundational building block for health. “Start with fiber first,” she advises. “That means eating more whole grains, beans, leafy greens, and even mushrooms. Add more of these foods to your plate and make sure you’re getting fiber with every meal.”

Why Fiber Matters More Than You Think

Fiber plays a pivotal role in regulating digestion, helping to prevent constipation and promoting a healthy gut microbiome. It also helps control blood sugar levels and can reduce cholesterol, making it a key component in preventing heart disease.

But fiber does more than just support digestive health. Amati explains how it can influence the entire body, including mental well-being. “A healthy gut can support better mental health, reduce inflammation, and even impact heart disease,” she says. Fiber-rich foods feed the beneficial bacteria in our gut, which are essential for overall health.

The gut microbiome, an ecosystem of bacteria living in your intestines, affects everything from your immune system to your mood. “We now know that the gut microbiome is central to many aspects of health, and fiber is the best way to support it,” Amati adds. Fiber helps feed these bacteria, encouraging a diverse and healthy microbiome, which in turn supports the body’s immune response and even brain function.

While fiber should be a priority, Amati is quick to point out that no single nutrient can make or break your diet. Healthy eating isn’t about obsessing over one aspect, like fiber or protein, but about creating a balanced dietary pattern that supports your overall health.

One of the most compelling examples of common-sense eating backed by science is the Mediterranean diet.

“We often hear things like ‘carbs are bad’ or ‘proteins are good,’ but the truth is, we don’t eat nutrients in isolation,” she says. “We eat a diet, which is a combination of many foods over time.” Instead of focusing on what’s on your plate at every meal, she recommends paying attention to your long-term eating habits.

“Look at the overall pattern of your diet,” Amati explains. “It’s not about what you eat on any given day, but what you’re consistently eating week to week, month to month. Focus on adding more of the good stuff, like fiber-rich foods, and you’ll naturally push out the less healthy options.”

The Mediterranean Diet: A Science-Backed Eating Pattern

One of the most reliable examples of a balanced, fiber-rich diet is the Mediterranean diet, which Amati strongly advocates.

The Mediterranean diet is not so much a strict menu as it is a general pattern. It’s rich in fruits, vegetables, whole grains, legumes, nuts, and healthy fats like olive oil, with less dairy and meat. There’s a mountain of research backing this up, Amati mentioned in a panel at the Hay Festival.

“It has evidence across all health outcomes. There’s hundreds of studies. We have the epidemiological data. When we follow people across a long period of time and track what they’re eating, people who follow it tend to live long and have the best health outcomes, it’s really clear now.”

Amati is clear that adopting the Mediterranean diet doesn’t mean making drastic changes overnight. The key is to implement small, sustainable changes. For example, you can start by replacing processed snacks with nuts or adding more leafy greens to your meals. You don’t have to overhaul everything at once.

She also cautions against being too rigid. If you’re at the airport or somewhere where you don’t have Mediterranean diet food, that’s fine. If you want a burger every now and then, that’s not a tragedy. “It’s the long-term pattern of what you eat that matters, not what you ate on any given day.”

Gut bacteria and ultra-processed foods

If there’s one thing you should be wary of, however, it’s ultra-processed foods.

Ultra-processed foods are a growing concern in modern diets. But here’s the thing: it’s pretty hard to even define what they are. Some things, like fizzy soda and potato chips, are obviously ultra-processed foods (UPFs). But other things, like sweetened breakfast cereal or even some deli meats, don’t scream “UPF” and can trick consumers.

Amati told us that a good way to think about it is that ultra-processed foods are “industrially produced convenience foods” that are typically made in factories, heavily packaged, and loaded with marketing messages designed to make them appealing.

The key characteristic of ultra-processed foods, she says, is that they contain ingredients you would never use at home, such as gums, emulsifiers, sweeteners, and colorants. If a food contains additives or extracts you wouldn’t have in your own kitchen, it’s likely to be ultra-processed.

For example, she highlights that even seemingly natural options, like “100% natural chicken breast skewers,” often contain dozens of unnecessary ingredients when you check the label. Instead, she advises preparing whole foods yourself, like buying a simple chicken breast and seasoning it at home.

As Amati explains, the gut microbiome — essentially the ecosystem of bacteria living in your intestines — plays a critical role in your overall health, influencing everything from mental health to immune function.

“We now know that a healthy gut can support better mental health, reduce inflammation, and even impact heart disease,” she said. Amati also points to basic things like eating fiber-rich fruits and veggies, but she also says that fermented foods like sauerkraut, kimchi, and kefir can help our gut microbiome.

“Fermented foods are rich in probiotics, which help support a healthy microbiome,” she says. “Including these foods in your diet, even in small amounts, can make a significant difference.”

Cut through the noise, follow science-backed advice

The message from Federica Amati is clear: common sense eating, supported by scientific evidence, is still the best way to improve and protect your health. While flashy diets and extreme advice may catch attention on social media, they often lack the research to back them up.

“Nutrition doesn’t have to be complicated,” she says. “At the end of the day, what works are the simple things — more vegetables, more whole grains, less processed food. It’s about creating habits that are sustainable for the long term.”

Federica Amati’s new book, “Every Body Should Know This: The Science of Eating for a Lifetime of Health” is available on Amazon.

You can watch our entire interview with Federica Amati on Youtube.