Meal prepping is the ever so slightly smug Instagram craze for preparing all your weekday meals in advance.

It's an efficient way for health and fitness fanatics to make sure they still eat the right foods when pressed for time.

But if you're looking to join the masses of people who meal prep every week as they try to achieve their weight loss goals, then you need to know the best foods to fill your plastic containers with. 

A new graphic helpfully illustrates exactly how you should pack up your lunchboxes if you are trying to stay trim or lose weight. Meals prepped in advance don't need to be complicated and says they just need to contain a minimum of three ingredients.

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The blog advises you to fill lunchboxes with three essential food groups: lean protein, vegetable, and starch, as well as a healthy fat.

Meal prep bloggers suggest planning out your meals two to three days before you want to start preparing your food so you can go out and buy just the ingredients you need, rather than be tempted by impulse buys. As for the ingredients, the MealPrepOnFleek bloggers suggest a large range of lean proteins, vegetables and starches that you can fill your lunchboxes with.

All the ingredients can be mixed and matched. MealPrepOnFleek suggests a combination of salmon, quinoa, and spinach, or chicken, kale and rice.

Then all that's left to do is cook your food and fill your boxes, which can be done on a Sunday or Monday – the most popular days for meal prepping.

Just be careful with certain proteins such as fish, which only keep for a maximum of two days once cooked. But you shouldn't be stuck for inspiration, as Instagram is full of mouthwatering images of prepped food under the #mealprep and #mealprepdaily hashtags.

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In fact, there are more than 4.5 million photos tagged using the #mealprep hashtag. The only downside to the meal prep craze is that it does require a lot of planning not to mention a lot of plastic containers to keep your food in.

But meal preppers swear by the craze, and it could be a good way to stick to your healthy eating ambitions and lose weight.