Fad diets may be bad for you

With these three fad diets popping up on our radar recently, we spoke to an expert to find out what exactly they entail and if they are worth trying.

THE KETO DIET

What is it: The diet - developed in the 1920s - practically eliminates carbs, so they make up just 5 per cent of your daily calorie intake.

That translates to between 90 and 100 calories from carbs. For perspective, a bowl of white rice is 200 calories.

If you are new to this, dietitian Bonnie Lau of digital health company Holmusk suggested taking it slow and cutting your carb intake to about a quarter of what you usually eat.

That means skipping starches like potatoes, bread, grains and even fruit. Load up on meat and lots of healthy fat.

How it works: Because you are consuming fewer carbs to burn as energy, your body burns fat instead.

When you are on this diet, fat gets converted into a compound known as ketones to be used as fuel, said Ms Lau.

Be warned though: This diet could backfire. You might have trouble concentrating or suffer from constipation.

Without grains and fruit, you might not get enough nutrients and fibre in your diet.

To prevent this, Ms Lau suggested "carb cycling", which means altering your carb intake according to your needs. So if you are working out that day, up your carbs.

As for the kind of meat, go for lean meat. Fatty meat has saturated fat that increases your risk of heart disease.

Skip this if: You have chronic conditions such as diabetes or you are on medication, said Ms Lau. Check with your doctor first.

Torture level: 5 out of 5

At first you feel great because of that free pass to eat meat and fatty foods.

But the absence of carbs will haunt you - like when all you want is a big cheeseburger with lots of fries.

THE LECTIN-FREE DIET

What it is: Lectin is the protein said to be responsible for causing gut problems. It is found in just about everything. We are talking beans, legumes, quinoa and nuts, spices like peppermint and nutmeg, fruits and vegetables like potatoes, tomatoes, eggplant, berries, watermelons, corn (even corn-fed meat) and coffee.

Legumes and wholegrain foods contain the highest amount of lectin, said Ms Lau. This diet was popularised by US heart surgeon Steven Gundry.

How it works: The theory is that lectin binds to the cells in your gut and blocks the absorption of nutrients. This can affect your immune system and make you sick. But Ms Lau said there is no proof that a lectin-free diet helps with weight loss.

In fact, soaking legumes and grains in water and cooking them thoroughly reduces the lectin significantly and prevents potential digestive problems.

The diet is easy for people who hate vegetables, but is not particularly healthy. You don't get much fibre and have to make up for the lack of nutrients with expensive supplements.

Skip this if: You enjoy your food. Ms Lau does not encourage anybody to try this diet.

Torture level: 3 out of 5

Basically, you need a great memory for the laundry list of things you can't eat.

THE PEGAN DIET

What it is: This one's the new kid on the block, having emerged in 2014. It is the brainchild of Dr Mark Hyman, director of the Cleveland Clinic's Center for Functional Medicine.

Think of the pegan diet as a mash-up of the paleo (eating what our hunter-gatherer ancestors did - which means no high-fat, sugary and processed foods) and vegan philosophies. This might sound counter-intuitive, but it is essentially a vegan diet that lets you eat meat.

Plant-based food should make up most of your intake, and you should think of meat as a side dish. You will also have to skip processed foods as well as dairy, whole grains, legumes and some fruit (like dates and grapes) all of which are believed to be "harmful to the body", said Ms Lau.

How it works: Your staple food group is vegetables. This keeps the calorie count low. You are also encouraged to have healthy fats such as avocado, nuts and seeds. These fatty foods help you stay full for longer. Apart from offering possible weight loss, the diet also cuts out high-sugar and highly processed foods that can lead to diabetes and other diseases.

However, you are at risk of nutritional deficiencies.

You might not be getting enough protein. And without dairy, you may not get enough calcium and vitamin D either.

Fewer carbs (since gluten and grains are out) might also mean that you end up with low blood sugar, which can cause you to feel dizzy or nauseated.

Skip this if: You are super active or athletic, and need a protein-rich diet to keep going.

Torture level: 2 out of 5.

If you like your veggies, you will be all right.