Nutrition advice is full of myths, from “carbs make you fat” to “frozen vegetables aren’t as healthy as fresh.” Below, we check 10 common ones against the evidence. The short version: no single food or nutrient makes you gain weight or keeps you healthy on its own; overall eating patterns, portion sizes and food quality matter most. Many popular “rules,” such as eating every 2 to 3 hours, cutting out gluten or detoxing with juices, aren’t supported by good evidence for most people.
Myth 1: Carbs make you fat
The facts: weight gain comes from eating more energy than you use, whether from carbs, fat or protein. In the DIETFITS trial, people following a healthy low-fat or a healthy low-carb diet lost similar amounts of weight after 12 months. The type of carbohydrate matters for health: whole grains, beans, vegetables and fruit are linked with better health, while sugary drinks and refined carbs aren’t. Our comparison of keto vs calorie counting explains more.
Myth 2: Eating fat makes you fat
The facts: fat is the most energy-dense nutrient, so it’s easy to overeat, but it doesn’t cause weight gain on its own. The type matters more than the amount for heart health. The NHS advises cutting down on saturated and trans fats and replacing some of them with unsaturated fats, such as olive oil, nuts and oily fish. Our guide to healthy fats explains which to choose.
Myth 3: Fresh vegetables are always better than frozen
The facts: frozen vegetables and fruit are usually frozen soon after harvest, so they keep their nutrients well, and sometimes contain more than “fresh” produce that has spent days in transport and storage. The NHS counts frozen and canned fruit and vegetables toward your 5 a day. Our guide to seasonal eating covers this.
Myth 4: Eating late at night always causes weight gain
The facts: total intake over the day matters most. But timing may play a part: in a controlled study where people ate the same meals earlier or later in the day, late eating increased hunger and lowered energy expenditure. A large meal right before bed can also disturb sleep and cause heartburn. Our article on eating late at night explains the evidence.
Myth 5: You need to detox your body
The facts: your liver, kidneys and gut remove waste continuously. The US NCCIH notes that a review found no compelling evidence that detox diets help with weight management or removing toxins. Our article on whether detox diets work covers the risks too.
Myth 6: Gluten-free is healthier for everyone
The facts: people with coeliac disease must avoid gluten completely, and the NHS explains that a gluten-free diet controls symptoms and prevents complications. For everyone else, there’s no evidence that cutting out gluten is healthier. Many gluten-free products are lower in fiber and higher in sugar or fat. If you think gluten affects you, see your doctor before cutting it out, because coeliac tests are only accurate while you’re still eating gluten.
Myth 7: Eating small meals every 2 to 3 hours boosts your metabolism
The facts: the energy you use digesting food depends on how much you eat in total, not how often. Three meals a day or six smaller ones can both work. Choose the pattern that keeps your hunger and energy steady.
Myth 8: Brown sugar and honey are healthier than white sugar
The facts: they all count as free sugars, which the NHS advises limiting to 30 g a day for adults. Brown sugar and honey contain only tiny amounts of minerals. Our guide on how much sugar per day explains the limits.
Myth 9: Eggs are bad for your cholesterol
The facts: for most people, the cholesterol in food has a smaller effect on blood cholesterol than saturated fat does. Eggs can be part of a healthy diet; how you cook them, and what you eat with them, matters more. The NHS advice on lowering cholesterol focuses on cutting saturated fat, eating more fiber, and being active. Our guide to foods that lower cholesterol has more.
Myth 10: You must drink 8 glasses of water on top of everything else
The facts: the NHS recommends 6 to 8 cups or glasses of fluid a day, but this includes tea, coffee, milk and lower-sugar drinks, and food provides water too. Needs vary with activity, climate and body size. Pale yellow urine is a good sign you’re drinking enough. Our guide on how much water to drink explains more.
How to spot a nutrition myth
- It sounds too simple: one food that “melts” weight or “cures” disease.
- It bans whole food groups without a medical reason.
- It’s based on one small experiment, especially in animals or a test tube.
- It’s selling something, such as a supplement, tea or program.
- It uses vague words like “toxins,” “clean” or “superfood” without explaining them.
Our guide on how to judge nutrition headlines explains more.
Common questions
Is it true that some foods have “negative calories”?
No. Foods such as celery are very low in calories, but digesting them doesn’t use more energy than they provide. Our article on whether celery is good for you explains more.
Where can I find reliable nutrition advice?
National health services, such as the NHS, government health agencies, and registered dietitians are good sources. Our guide to the difference between a dietitian and a nutritionist explains who to trust.
Why does nutrition advice keep changing?
Science builds over time, and early findings are sometimes overturned by bigger, better-designed experiments. The core advice, eating plenty of plants, whole grains and fiber and limiting sugar, salt and ultra-processed foods, has stayed remarkably stable.
Are calories all that matter?
For weight, they matter most. For health, the quality of your food matters too.
This article is general information, not medical advice. Talk to your doctor or a registered dietitian before making big changes to how you eat, especially if you have a health condition, take regular medication, or are pregnant or breastfeeding.
