Diet pros and cons

Our WCRF UK nutritionist looks at the pros and cons of popular diets.

After not smoking, maintaining a healthy weight is the most important thing we can do for cancer prevention. If you are unsure about whether or not you’re a healthy weight, try our BMI calculator.

Often, we look for quick-fix solutions to losing excess weight. But evidence shows that diets which call for extreme calorie cutting or unbalanced meals are unlikely to achieve long-term weight loss. A better approach is to make small, life-long adjustments to the food you choose and the amount of physical activity you do.

There are so many diets on the market, each claiming to be the one that works! But are any of them any good? Here, we aim to dispel the myths of some of the more well known diets.

The Atkins Diet

The South Beach Diet

The Atkins Diet

What is it?

The Atkins Diet was created by Dr Robert Atkins, an American physician and cardiologist. The diet is based on his theory that by severely limiting carbohydrate intake, the body will first use up any carbohydrate stores as fuel, and then use fat stores as fuel for energy instead (a state called ketosis), thereby leading to weight loss.

The first phase of the programme begins with having a very low intake of carbohydrate to put the body into a state of ketosis. It lasts for 14 days and consists of a daily diet of 100g protein, 75g fat and less than 20g carbohydrates (which includes starch, sugar and fibre).

The next phase is an ongoing weight-loss phase, where carbohydrate intake is limited to less than 30g per day (the equivalent to two slices of bread). This is followed by a pre-maintenance and maintenance phase where carbohydrate intake can be increased to 120g per day (equivalent to eight slices of bread).

The pros and cons

Pros:

• Strictly following this diet does tend to lead to weight loss.

Cons:

• The diet is only effective whilst you are following it. As soon as carbohydrate-intake is increased, the weight returns quickly. This means it tends to be a short-term solution for weight-loss, as it can be difficult to stick to for long periods.

• A high-protein diet such as this can lead to eating too much red and/or processed meat. To reduce your risk of bowel cancer WCRF UK recommends that we have no more than 500g (cooked weight) per week of red meat (such as beef, pork and lamb) and avoid processed meats (such as bacon) altogether. A medium steak (145g) contains about 44g protein, so two steaks would contain the daily Atkins protein allowance of 100g (nearly 300g red meat).

• The diet restricts carbohydrate intake, which means eliminating or dramatically reducing the intake of starchy vegetables, fruits, beans, bread, rice, cereals, pasta and other grain products, leaving a very limited diet, primarily of fat and protein. Vital nutrients from vegetables, fruits and wholegrains that help reduce your risk of cancer will therefore be absent.

• The long-term health effects of following the Atkins diet are not yet known, but an increased risk of cancer and heart problems in the future are possible.

• Carbohydrate stores are needed to fuel physical activity, which helps reduce the risk of cancer.

The most sensible ways to manage your weight and reduce your cancer risk are to:

1. Avoid sugary drinks and limit energy-dense foods.
2. Aim to take 60 minutes or more of moderate activity, or 30 minutes or more of vigorous activity, every day.
3. Choose a diet based around plant foods. Aim to fill at least two-thirds of your plate with vegetables, fruits, cereals and grains, and then add one-third or less of animal foods.

Get more information on how weight affects cancer risk.

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The South Beach Diet

What is it?

This was created by Dr Arthur Agatston. Being a cardiologist, he put together an eating plan with the aim of promoting a healthy heart, and later called it the South Beach Diet.

This diet is low in carbohydrate, but unlike some other low-carb diets, it distinguishes between carbohydrates as being ‘good’ or ‘bad’ based on how they affect your blood sugar levels.

The diet is split into three phases. In terms of what you ‘can’ and ‘cannot’ eat, the phases become more relaxed as they go on. Phase one is the ‘strict’ phase, which excludes all bread, rice, potatoes, pasta, baked goods and fruit. This phase lasts for fourteen days.

Phase two lasts as long as it takes you to lose your desired weight and involves re-introducing some of the ‘good’ carbohydrates, like wholegrain bread and some fruits. Compared to phase one, the rate of weight loss slows down a little because the aim is to continue losing weight whilst increasing carbohydrate intake. You need to monitor your weight and monitor how you react to different carbohydrate-containing foods.

Phase three begins when you have reached your target weight and is supposed to last indefinitely. It’s goal is maintenance of your weight through eating a balanced diet. It is built on the same principles as phases one and two, but it allows more frequent indulgences. The idea is that by this stage, cravings for ‘bad’ foods will normally be minimal, as you will have already settled into an eating plan that you're happy with.

The pros and cons

Pros:

• The diet sets out to provide a system where you get to know your own weight loss patterns and how you react to certain foods. Knowing your own body is one of the key things that help us towards successful and long-term weight management.
• The idea is that you are able to maintain a healthy weight by switching between the different phases when needed. For example, if you put on some weight during phase three, you can go back to phase two until you’re back on track again.
• Phase three is based around a balanced diet and so encourages you to avoid energy-dense foods that can lead to weight gain.

Cons:

• Phase one requires a lot of foods, like bread, rice and fruit, to be cut out of your diet. Eating a variety of vegetables, fruits, wholegrains and pulses such as beans is important for cancer prevention.
• Phase one of the diet is very strict and lasts for two weeks so there is a good chance you might not keep it up and end up feeling like a ‘failure’. This can discourage you from trying to lose weight further, thinking it’s a dead-end battle. In fact, just by making small changes to our diet and the amount of physical activity we do, we can lose weight and learn how to manage our weight in the long-term.
• The diet doesn’t promote the importance of being physically active for weight management.
• You may feel that you can over-indulge during phase three and when you put on weight, make up for it by going back a phase or two. This could lead to ‘yo-yo dieting’.

The most sensible ways to manage your weight and reduce your cancer risk are to:

1. Avoid sugary drinks and limit energy-dense foods.
2. Aim to take 60 minutes or more of moderate activity, or 30 minutes or more of vigorous activity, every day.
3. Choose a diet based around plant foods. Aim to fill at least two-thirds of your plate with vegetables, fruits, cereals and grains, and then add one-third or less of animal foods.

Get more information on how weight affects cancer risk.

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