Trying to reshape your diet and lifestyle habits? That’s a great goal to have, but don't let your plans to get healthier and achieve the weight you’re happy with get waylaid by bad dieting advice. Here are 21 nuggets of weight loss "wisdom" to definitely ignore – and what to do instead.

Juicing removes the fibre from fruit and veg and also releases the sugars from inside plant cell walls. These free sugars can harm teeth and raise blood sugar just like added sugar. More than this, a juice cleanse doesn’t contain enough protein to prevent muscle being lost. "150ml (5 fl oz) of juice daily provides vitamin C and phytochemicals but drinking only juice is not a sensible way to lose weight or be healthy," says registered dietitian and British Dietetic Association spokesperson Helen Bond.

Unfortunately, calories burned in exercise doesn’t equal extra calories to scoff. That’s because many of us compensate, often unconsciously, by eating more or burning fewer calories during the rest of the day on workout days – we may lie down more, fidget less or not walk about as much, for example. In short: the benefits of exercise are huge, but weight loss isn’t one you can necessarily count on.

US television host Bill Maher recently suggested on his HBO show Real Time that fat-shaming should make a comeback. The reality? Every bit of evidence suggests fat shaming just makes people fatter and sicker, according to an editorial in CMAJ (Canadian Medical Association Journal). Internalised weight bias – the fat-shaming you do to yourself for not looking a certain way is the most damaging of all, so give yourself a break.

If this way of eating suits you, then fine. However, a rigorous scientific analysis in a Dutch university that compared diets of equal calories but differing carbohydrate and fat content found that both regimes produced very similar body fat loss. In fact, lower fat diets with at least 100 grams (3.5oz) of carbohydrate daily (the amount in two slices of bread and a serving of pasta) had the slight edge over LCHF for preventing diabetes and obesity.

This even more extreme version of LCHF is gaining some followers who say it keeps them slim and satiated (you eat meat, fish, eggs and cheese and virtually nothing plant-based). But it goes counter to every possible healthy eating guideline. "You're not getting fibre for a healthy gut, you could miss out on vitamin C and your saturated fat intake, which is bad for the heart, will be through the roof," says dietitian Helen Bond. In short, it’s a diet to leave well alone.

This well-meant advice can stop you eating an ultra-processed diet, which in one study was linked with weight gain. But some tongue-twister names are perfectly healthy, such as added fibre, vitamins or preservatives to prevent food poisoning. The main problem with scouring every ingredient list is that it creates guilt about foods that aren’t "clean", creating an unhealthily obsessive relationship with food.

When it comes to how sated you feel and how soon you will want to eat again, two similar calorie counts can have very different effects. "Imagine a croissant versus two poached eggs with grilled mushrooms on a slice of whole grain toast and you get the idea," says Dr Schenker. "They both have around 280 calories, but the egg on toast will satisfy for longer and provide much better nutrition too."

It’s equally nonsense to say that you can ignore calories completely. "It’s a great idea to put the nutritional quality of your diet first and foremost, but you do still have to take calorie intake into account if you want to lose weight," says Dr Schenker. The bottom line? To lose weight, you always have to eat fewer calories than your body uses up.

Grazing used to be promoted quite heavily as a way to manage weight – the logic being that you control your hunger better, preventing binges, this way. But grazing doesn’t produce better weight loss, according to research, and grazers may have higher levels of unhealthy blood fats.

On the other hand, being a natural snacker doesn’t have to spell disaster for your diet either. "Planned, portion-controlled snacks that keep you going between meals can help some people," says Helen Bond. The secret is to make snacks filling and nutrient rich – try a handful of nuts, a couple of tablespoons of hummus with carrot sticks or fruit and yogurt – and to eat slightly less for your main meals.

Actually, meal replacement shakes and snacks can produce successful weight loss, especially when fighting obesity. Oxford University researchers found that on average people who dieted using meal replacements lost 7.2kg (1st 1lb) more than people using other diets after one year. Strict rules govern the manufacture of weight loss meal replacements, which must contain a full range of vitamins and minerals and high levels of protein and fibre for fullness.

Cutting down your carb portion size – especially white rice, bread and flour – is a good idea. But some carb-rich foods, including whole grains, beans and lentils, are rich in phytochemicals and fibre that help maintain a healthy gut microbiome, which in turn can manage weight and support the immune system. A whole grain-rich diet also increases resting metabolic rate and the amount of calories you excrete, according to research.

If you’ve had a dysfunctional relationship with food, the scales may be triggering, but for everyone else, getting on the scales regularly – once or twice a week – is a great way to keep an eye on your weight and nip any swings upward in the bud. Weighing regularly is a common trait among people in America’s National Weight Control Registry, a database of people who lost at least 13.6kg (30lbs) and kept it off.

The claim that coconut oil helps weight loss is based on its content of MCTs – medium chain triglycerides ­– which may slightly boost metabolism. But most studies used pure MCT oils, not coconut oil, which also contains a lot of myristic acid, a type of fat that significantly raises cholesterol. Each tablespoon of coconut oil also contains 120 calories, so won't aid weight loss unless you’re cutting down significantly elsewhere.

Low carb extremists claim eating a banana is equivalent to eating six teaspoons of sugar. But the bendy fruits have a low/medium glycaemic index (GI) – which means the sugars in them release only slowly, especially if you eat them just ripe. They also have lots of potassium, vitamin B6 and fibre. A large Harvard University study that looked at the relationship between fruit and veg intake and people’s weight found consumption of several fruits, including bananas, correlated with less weight gain.

"You don’t need special cleansing diets and will do much better by just eating a healthy diet with lots of fruit, vegetables, plant proteins and fibre, so your body’s own natural detoxification system can do its job optimally," says Dr Schenker. A healthy liver and kidneys constantly cleanse the body by filtering the blood and screening out toxins without the need for a detox programme.

These 20 foods will boost your immune system

Sugar is sugar in whichever form it comes. Even if less refined forms do have slightly more nutrients, such as potassium and iron, the quantities are really tiny and you don’t eat sugary food for its nutrients anyway.

If you have an actual diagnosis of gluten intolerance or sensitivity, then of course you need to cut out this wheat protein. But if not, steer clear of gluten-free products as they tend to be higher in calories, a survey found. They may also be lower in fibre, iron, B vitamins and minerals.

Take a look at 20 "healthy" foods nutritionists say to steer clear of

Reducing added sugar is a good idea as it supplies calories without nutrients but it’s not a guaranteed route to weight loss. For example, a bowl of Frosties and a bowl of corn flakes have identical calorie counts (113 to be precise) and there are more calories in a handful of nuts than a handful of Haribo jelly sweets. Focusing on cutting portion sizes, while not denying yourself the occasional enjoyable treat that might be high sugar, is a better bet for weight loss.

These are 28 of the world's highest sugar cereals

Breakfast eaters tend to eat better overall, but that doesn’t mean a hearty breakfast is a route to weight loss. In fact, research at the University of Munich found that people who ate a big breakfast didn’t eat less at lunch and consumed 400 calories more over the whole day. "Not having breakfast is not a nutritional sin if it works for you and you make healthy choices the rest of the day," says Dr Sarah Schenker, author of Eating Fat Will Make You Fat: And Other Human Body Myths Busted.

Alkaline diet advocates say you can make your blood more alkaline by eating a specific balance of foods and that this will help weight loss as well as reduce cancer and osteoporosis risk. But the British Dietetic Association says the alkaline diet is based on a "basic misunderstanding of human physiology." The bottom line? You can’t change the pH of your blood and wouldn’t want to – it has to be kept within strict limits for good health.

Now discover our 25 best-ever healthy cooking hacks