If you're looking to try a weight loss diet such as keto or intermittent fasting, your success may depend on the diet you choose. And let's face it, the high number of available diets for weight loss can be overwhelming.
There are many factors to consider when it comes to finding an eating plan that suits you. Is it practical for your current lifestyle? Will you feel satisfied? Will it help you to create lasting change?
Thanks to its flexible approach that's backed by more than 90 clinical trials showing long-term effectiveness, WW has been rated #1 Doctor-recommended behavioral weight-loss programme.* Because the programme doesn't cut out any food groups, you still have the freedom to enjoy all the foods you love while living a healthier lifestyle.
If you were thinking of trying some of the trending diets out there, here's some guidance on how they can help you reach your health and weight loss goals...
*Based on a 2020 IQVIA survey of 14,000 doctors who recommend weight-loss programs to patients.
1. The keto diet
It involves
Eating a diet that's very low in carbohydrates and moderate in protein, so that 70 to 80% of your total energy intake comes from fat.
The theory is
That if you deprive your body of its main source of energy (glucose from carbohydrate-containing foods), it goes into a state of ketosis, where it burns fat stored in the body for fuel instead. During this process, by-products called ketones are produced, which are then used by the body's muscles, tissues, and brain.
The science says
That a ketogenic diet may benefit people living with specific health concerns, including epilepsy, some types of cancer and even dementia. Some studies have shown it can also result in short-term weight loss, as well as delivering positive impacts on blood pressure, cholesterol levels, and blood sugar. But not only did a review study published in 2013 find that after a year, these effects weren't significantly different to those achieved via conventional weight loss methods, research has also shown that dropout rates are high among people following a keto diet because it's restrictive.
The bottom line
While restrictive weight-loss diets might work in the short term, the majority of people using them regain that weight, and often more, partly because restrictive behaviours and eating plans aren't sustainable. The carbohydrate restriction may cause nutritional deficiencies, fatigue, low mood, irritability, headaches, constipation, and 'brain fog'. Plus, because it takes valuable sources of fibre off the table, it may increase your risk of bowel cancer if it's used long term. There's also a risk that ketone levels can climb too high, causing a dangerous condition called ketoacidosis, where acid levels in the blood reach toxic levels.
NOW READ: WW vs. keto
2. 16:8 fasting
It involves
Fasting for 16 continuous hours, then being free to eat whatever you like for the other eight, every day. Currently, the most widely researched approach is taking the eight-hour eating window between 10am and 6pm.
The theory is
That it's an easier, more convenient way to lose weight than eating plans that require counting calories. Plus, like all intermittent fasting (IF) diets, it promises improvements in markers of health typically associated with an increased risk of disease, such as high blood pressure and high cholesterol levels.
The science says
That after 12 weeks, people doing the 16:8 diet lost three per cent of their body weight and had lower blood pressure. That's according to a small study – one of the few to put this form of IF under the microscope – published in June 2018. The 16:8 diet's impact on long-term weight loss isn't yet clear, but research into the dropout rates associated with all IF methods suggests that, in fact, they're no easier to follow and maintain than weight loss methods that require counting calories.
The bottom line
Watching the clock rather than what you eat might sound easier, but, as well as the risk of feeling excessively hungry towards the end of the 16-hour fast, not being able to eat after 6pm can seriously limit your lifestyle, making it hard to achieve every single day. And, while simply delaying the eating window might seem like a fix, IF experts don't recommend it. As with all IF diets, concerns have also been raised that people will 'overdo' it during the non-fasting period (although the most recent 16:8 research suggests this doesn't happen), that they don’t promote or support healthy food choices and may even encourage unhealthy behaviours, such as an increased fixation on food.
3. Alkaline diet
It involves
Limiting your intake of foods that have been labelled as 'acid forming', like meat, fish, dairy, grains, alcohol and highly processed foods and refined sugars, while bumping up your intake of alkaline forming foods, like fruit and vegies. You can also buy alkaline water to drink.
The theory is
That by doing this, you can regulate your body's pH level, lowering its acidity to reduce inflammation and protect against osteoporosis and a range of other chronic diseases. Increased weight loss is said to be another side effect of making your body more alkaline.
The science says
That sticking to an alkaline diet can lower the acidity of urine, which may discourage the growth of the bacteria responsible for urinary tract infections. However, it won't affect the pH of your blood or your body. So, while a 2012 review study did make the connection between eating an alkaline diet with better bone and muscle health and even a reduction in back pain, more recent research questions those claims, finding it has no bearing on serious diseases like osteoporosis or cancer. In fact, according to research published in 2017, there is no high-quality evidence to support the idea that dietary acid changes the body's pH or causes disease.
The bottom line
While some of the dietary advice the alkaline diet promotes, like cutting back on highly processed foods and alcohol, and eating plenty of fruit and veggies, is healthy, a lot of them aren't. Removing foods like fish, wholegrains, lean meats, and low-fat dairy is not only restrictive, it eliminates valuable sources of essential vitamins and minerals, which risks dietary deficiencies. Plus, while the reduction in calories created by eating mainly fruit and veggies might lead to short-term weight loss, this isn't backed up by credible studies and isn't sustainable in the long term.
4. Blood type diet
It involves
Tailoring your diet to suit your blood type. So, while people with type O blood are prescribed a diet rich in animal protein but light on grains, type As should stick to a vegetarian diet. Types B and AB should eat slightly differently again.
The theory is
That your blood type reflects your ancestry, and that people with different blood types process food differently. Eating the 'right' diet for your blood type means you're eating the way your ancestors did, which can improve health and decrease the risk of chronic diseases, like heart disease.
The science says
That while your inherited blood type may have a role to play in increasing or decreasing the risk of heart disease, as well as some types of cancer, research has failed to prove that what you eat has any influence over this. In fact, not only did a 2013 review of more than 1400 blood type diet studies report that no evidence currently exists to validate the supposed health benefits of this eating plan, research released in 2018 went further, stating that the theory behind this diet just doesn't stack up.
The bottom line
All four of the blood type eating plans focus on nutritious recipes, over heavily processed, refined ones, which explains why in a 2014 study, they delivered improvements on heart disease risk factors like waist circumference and blood pressure. But that same study showed that the improvements were independent of blood type – so everyone eating the type-A diet benefited, regardless of their blood type. Plus, not only are all four of the eating plans restrictive in their own ways, they also all eliminate whole food groups, which could lead to dietary deficiencies in vital nutrients.
5. Mediterranean diet
It involves
Sticking to a plant-based diet, which means eating wholegrains, olive oil, fruits, veggies, legumes, nuts, herbs and spices on a daily basis. Animal-based proteins like eggs and dairy should be eaten a few times a week, fish or chicken twice weekly, and red meat just a few times a month.
The theory is
It's a diet that mimics how a population eat in a part of Greece that's been identified as one of the world's Blue Zones, a collection of five geographical regions that are home to the world's longest-lived people.
The science says
That eating like they do in the Mediterranean does have a number of impressive health benefits. Among other things, research shows it lowers the risk of heart disease by 47 per cent over a 10-year period, offers some protection against age-related brain shrinkage, and may deliver higher muscle mass and bone density after menopause. A large study of more than 10,500 women also found that those who followed a Mediterranean-style diet were 46 per cent more likely to age healthfully, as a result. When it comes to long-term weight loss, a 2016 review of five trials discovered that sticking to a Mediterranean diet was more effective than low-fat diets for delivering and maintaining weight loss past 12 months, although it didn't perform any better than most other weight loss diets.
The bottom line
The Mediterranean diet has a lot going for it. Something to watch out for is that, because there's no consensus on specific amounts of foods or portion sizes, there's a chance it could lead to weight gain given that there's a strong emphasis on foods that are rich in fats, albeit healthy ones. That said, a study published two years ago suggests any weight gain associated with eating the high-in-healthy-fat Mediterranean diet isn't likely to be significant. The other thing to remember is that enjoying the health benefits associated with the Mediterranean diet relies on eating the entire combination of the foods it encourages, rather than any one or two in isolation. Without a specific structure to follow, some people may find achieving that, as well as the reliance on daily plant-based meals, tricky to achieve.