The truth about meal replacement diets

Most of us gain weight over Christmas, and come January the annual battle of the bulge begins. If you're thinking of trying meal replacement products, here's what you need to know.

See also: Six reasons why you can't lose weight

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If you struggle to control how many calories you eat, meal replacement diets offer a simple solution. Instead of having to worry about what to cook and eat, you have a set number of meal replacement products each day. These can include shakes, soups, bars and "powder" versions of everyday dishes, such as spaghetti Bolognese and shepherd's pie, that you simply add water to and microwave.

Some plans have VLC (very low calorie) options, such as the Cambridge Diet, Lighter Life, and Exante, where you consume under 800 calories a day. After you have lost weight initially, you are then encouraged to increase your calorie consumption and introduce normal, healthy meals into your diet.

Other plans encourage you to have two replacement meals (typically breakfast and lunch) and then have a healthy meal in the evening of around 500 calories. Some plans also allow two to three 100-calorie snacks a day.

As a general rule, if you consume around 1,200-1,400 calories each day you can expect to lose 1-2 pounds a week. Whichever plan you choose, it's important to drink a LOT of water – at least eight glasses a day.

Which plan is right for me?
There are lots of meal replacement programmes available, and it's often a question of trying a few products from each to decide which you like best. Slim Fast, Lighter Life and Celebrity Slim are available from large high street stores, such as Superdrug and Boots.

It often works out cheaper to order products online. Exante offer a wide range of discounts, with meal replacements costing under £1 each if you're happy to buy in bulk.

Do they work?
If you can stick to just the products and restrict your calorie intake, you will lose weight.

Several studies have shown that meal replacements are as good (if not better) as calorie-counted diets in terms at helping people lose weight in the short term. Research also shows that meal replacements are effective at helping people to maintain their new lower weight.

The main advantage is that meal replacement products are convenient and you don't need to think about cooking or counting calories, as it's already been done for you. However, if you enjoy cooking and like eating food, they can soon become monotonous (particularly if you're not eating real food as part of the plan).

Some plans have the advantage of weekly counsellors (such as the Cambridge Diet) who can offer you advice and support and keep you on track by weighing you each week. Lighter Life also runs group counselling sessions, which have proven to be very effective for many people. They also run phone sessions for those who can't get into a group.

As you would expect, these options are more expensive than simply ordering the products online or buying them in store.

Are meal replacement products healthy?
Meal replacement products are healthier than you might think. Most are well-balanced, providing a mix of all the nutrients your body needs – including 23 vitamins and minerals, and enough protein (at least 25 % of your daily requirement) and about 5g-6g of fibre.

Healthy eating guidelines recommend adults have 18g fibre daily and so two meal replacement products make a contribution to this – your proper meal of the day should contain lots of vegetables to make up the rest. You should also be eating lean protein in your evening meal.

What about the cons?
Aside from the potential monotony of flavours mentioned, meal replacement diets do little to educate people about their eating habits. Many people find that once they stop eating the products, they go back to how they ate before – and quickly regain all the weight.

For this reason, many programmes emphasise the importance of cooking and eating healthy meals while you are still taking the bars, shakes and soups, etc. Some people find that the 5:2 diet works well as a maintenance programme. Once you have reached your target weight, you eat a healthy diet for five days of the week, then have meal replacements for two days.

What do the experts say?
Thanks to a several studies supporting their use, health experts are more likely to recommend that obese people use them to lose weight. Organisations such as the National Obesity Forum, the British Dietetic Association and Dietitians in Obesity Management UK say meal replacements offer an alternative to other more conventional dietary treatments and may prove beneficial for some people.

However, they point out that additional support and advice needs to be given so that people can change the poor eating habits that caused them to gain weight in the first place.