The spring influx of diets has not stopped.

"Lose your belly by November 4!" is the most recent enticing subject line to hit my inbox.

Last week it was "Start your spring clean from the inside out" - a juice cleanse; $99 a day to eat nothing.

Isagenix - a meal replacement scheme - seems to be having a moment, too.

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I've observed the weird world of weight loss long enough now to recognise most faddish diets have a predictable series of things in common.

This has been true since the diet industry began. With each new diet, we see these features reappearing.

A science-ish sounding theory.

It always sounds plausible.

It often has scientific-sounding language and quotes research. It is often also touted as "revolutionary" or "radical".

• A drastic first "phase" in which the diet is extremely limited and strict.

I've seen this called an induction or attack phase. It is usually one or two weeks.

This seems designed to give you a quick initial weight loss, so you feel validated and stick to the plan.

There are usually a few more phases after this.

• Lists of banned foods.

You must not eat these! Sometimes they are obvious: sweets, cakes, sugary drinks.

But some seem completely arbitrary: I've seen diets banning cold water, peanut butter, tomatoes and chicken.

And then there are the diets that ban whole food groups such as dairy, grains or carbohydrates.

• "Magic" foods.

Sometimes there are foods or supplements you must take to make the diet work.

This is a red flag, especially if the magic food is a supplement you have to buy from the diet promoter.

Sometimes the magic food is a normal food.

The Dukan Diet has oat bran. The Morning Banana Diet has, obviously, bananas.

On the Grapefruit Diet you eat grapefruit before every meal with the theory that it contains enzymes that, when eaten before other foods, help burn off fat.

Science-ish, huh?

Then there's the bizarre HCG Diet, which has you taking pregnancy hormones and vitamin drops while following a very low-calorie eating plan (all yours from $129).

• Promises of huge weight loss; but not only that.

You will also get glowing skin; shiny hair; bright eyes; a better sex life.

• And the promise that it's EASY.

Fad diets are very often promoted as effortless. "Lose weight eating the foods you love!" is a common catchcry. "Never feel hungry!" is another. This is a lie.

What all diets also have in common of course, which we all know, is that they rarely work long-term.

Yes, you can lose weight eating any weird combination of foods. But eventually you'll have to come "off" the diet. And that's when - unless you're able to make a permanent change to how and what you're eating - the weight comes back.

Don't be sucked in.

The only winners here are the diet promoters, who are laughing all the way to the bank.