The British Dietetic Association has released a list of diets they say we should steer clear of in the new year.
They include the Raw Vegan, Alkaline, Pioppi and Ketogenic diets, as well as Katie Price's Nutritional Supplements.
Sian Porter from the BDA said: "If something sounds too good to be true, it probably is."
The British Nutrition Foundation agreed that the five diets are best avoided, while Dr Aseem Malhotra, author of The Pioppi diet, defended his meal plan.
Gwyneth Paltrow, Megan Fox and Sting have all come out in support of a vegan diet of uncooked foods.
Supporters define raw food as anything that has not been refined, canned or chemically processed, and has not been heated above 48C.
They argue that applying heat destroys some of the natural enzymes in food and that the body therefore needs to do more work to break the food down. They also say you lose nutrients through this process.
But Mrs Porter said: "People think that vegan is shorthand for healthy, but it requires careful planning to make sure you don't miss out on important nutrients."
The NHS suggests vegans consider taking vitamin B12 and vitamin D supplements.
Heat also brings out the nutrients in some foods, such as carrots while others, such as potatoes, cannot be eaten raw.
Tom Brady and the Duchess of York have been famous proponents of the alkaline diet.
The diet is based on the theory that you can change the pH balance (level of acidity) of your body and blood through the food that you eat - despite there currently being no substantial evidence to suggest that this is possible.
Advocates have claimed that high levels of "excess acid" in the body contribute to a range of health conditions including arthritis, osteoporosis, kidney and liver disorders, and even cancer.
They suggest eating "alkaline foods", primarily fruit and vegetables, to correct this.
But, according to Cancer Research UK, while eating more fruit and vegetables may help you lose weight, the pH of your food will not impact the pH of your blood.
Mrs Porter said: "So if it works to lose weight, it's because you're cutting down on calories."
The NHS says that the alkaline diet lacks evidence, and advises against cutting out whole food groups, as some versions of the diet suggest.
Katie Price - Nutritional Supplements
Katie Price has released a range of hydration, breakfast and meal replacement shakes.
According to the website, the drinks support muscle tone and maintenance as well as decreasing snacking and cravings.
Mrs Porter said: "The problem is people need to reintroduce food so you want something you can stick to."
While rapid weight loss can be motivating, the BDA said it is unsustainable and that appetite suppressors are not a healthy or advisable way of losing weight.
Sarah Coe from the BNF said: "Meal replacement products can be useful for people that have a lot of weight to lose, but should always be used under supervision from a health professional."
Katie Price Nutrition did not respond to a BBC request for comment.
The Pioppi diet claims to promote the principles of the Mediterranean diet to promote weight loss and reduce the risk of type 2 diabetes.
The authors, Dr Aseem Malhotra and Donal O'Neill, recommend a low-carbohydrate, high-fat diet with fruit and vegetables, fish, olive oil, alcohol in moderation and exercise.
They suggest intermittent fasting and discourage eating red meat, starchy carbs, and sweetened treats.
The BDA accused the pair of "hijacking" the Mediterranean diet with their agenda, saying it was "ridiculous" to include coconut oil or cauliflower for a pizza base as one of their suggestions.
Mrs Porter said: "We all know now that a Mediterranean-style diet is one of the most healthy diets to follow. But it's not low carb."
Mrs Porter added that the argument to eat a high level of saturated fat was based on evidence that had been "cherry-picked rather than looking at it in its entirety".
She said: "Why it might help you lose weight is because it's making healthier choices and you'd be having overall less calories."
But Dr Malhotra, a cardiologist and adviser at the National Obesity Forum, said: "The Pioppi Diet is an independent evaluation that marries the secrets of one of the world's healthiest villages with the latest medical, nutrition and exercise research to bust many myths prevalent in today's weight loss and health industries.
"It has received endorsements from a number of eminent international doctors, dieticians, Cochrane researchers and sports scientists.
"One has to question the financial links and influence of various food companies on the BDA. In my view, they cannot be trusted as an independent source of dietary advice."
In response to this, a BDA spokesperson said: "The analysis we release is always based on evidence and is unaffected by the important relationships we have with the nation's food producers.
"Our spokespeople, like all dieticians, are required to adhere to evidence-based practice as part of their registration with the Health and Care Professions Council."
A huge number of celebrities have been linked with this diet including Kim Kardashian, Kobe Bryant and Alec Baldwin.
The premise is to eat a very low carb, high fat, moderate protein diet, with carbohydrates coming from non-starchy vegetables, nuts and seeds.
The aim is to push the body into a state of "ketosis". Because it doesn't have the glucose from the carbohydrates, it instead breaks down fat to produce energy.
Ms Porter said: "The sinister thing here is people saying it can cure cancer and things like that - it absolutely cannot!"
She said by not eating carbohydrates, you avoid eating the calorie-laden things that generally accompany them: "If you're cutting out carbs, such as pasta, you're cutting out creamy sauce. If you're cutting out bread, you're cutting out butter. If you're cutting out biscuits, you're cutting out sugar."
The danger, she said, is that you can lose a lot of fibre from your diet which is important for gut health. Also, by removing whole grains from your diet you're depriving your body of many vitamins and minerals.
The BNF advises that it can be effective for losing weight in the short-term but this weight loss can be hard to sustain.
So how do I lose weight?
The BDA has a fact sheet recommending some of the best ways to lose weight. They suggest:
- Keep a food and mood diary to monitor how the two are connected
- Make a list of non-food related tasks you can do to distract you from thinking about food
- Set realistic goals: losing only 5-10% of your weight has massive health benefits
- Avoid eating at the same time as doing something else, such as watching TV, as this can cause you to overeat
- Half fill your plate with vegetables/salad and divide the other half between a protein and a starchy carbohydrate like potatoes or rice