Alkaline diet

The alkaline diet, whose celebrity fans reportedly include Gywneth Paltrow, Jennifer Aniston and Victoria Beckham, is based on the idea that our modern diets cause our body to produce too much acid. The theory is that excess acid in the body is turned into fat leading to weight gain. High acidity levels have also been blamed on conditions such as arthritis, osteoporosis, tiredness, kidney and liver disorders. The diet recommends cutting back on acid-producing foods such as meat, wheat and other grains, refined sugar, dairy products, caffeine, alcohol and processed foods in favour of “alkaline foods” – foods that reduce the body’s acidity levels – basically plenty of fruit and vegetables. The idea is that an alkaline diet helps to maintain the body’s acidity at healthy levels. There are different versions of the alkaline diet. Some followers adopt the "80/20 rule" consisting of a diet based on 80% fruit and veg and 20% grains and protein. Originally developed to help prevent kidney stones and urine infections by using diet to adjust the acidity levels in the urine, there is little evidence to support the diet’s more recent health benefits. The weight loss observed among followers is more likely down to eating plenty of fruit and vegetables and cutting down on sugar, alcohol and processed foods, which is standard healthy weight loss advice.

Pros:

The diet contains plenty of good healthy eating advice such cutting down on meat, avoiding sugar, alcohol and processed foods and eating more fruit and veg, nuts, seeds and legumes. This means that you will be cutting out foods you may normally eat and replacing them with healthier choices, which will also reduce your calorie intake.

Cons:

Your body regulates its acidity levels regardless of diet. When cutting down on dairy products such as milk, cheese and yoghurt you need to find other calcium substitutes, as cutting out an entire food group is never a good idea. Getting to grips with what you can and can’t eat on the diet can be time-consuming, particularly in the beginning.

BDA verdict:

The theory of the alkaline diet is that eating certain foods can help maintain the body's ideal pH balance (acidity levels) to improve overall health. But the body maintains its pH balance regardless of diet. The diet lacks evidence and some versions that advise cutting out entire food groups should be avoided. The more balanced versions of the diet provide variety and include all the food groups. If you are going to try the alkaline diet choose a balanced plan, stick to it to the letter and stay clear of supplements and other diet-related gimmicks.

    Cambridge diet

The Cambridge Weight Plans are based around buying and eating a range of meal-replacement products with the promise of rapid weight loss. There are six flexible diet plans ranging from 415kcal to 1,500kcal or more a day, depending on your weight loss goal. There is also a long-term weight management programme. The bars, soups, porridges and shakes can be used as your sole source of nutrition or together with low-calorie regular meals. While on the programme, you receive advice and support on healthy eating and exercise from a Cambridge adviser.

Pros:

Many people on very low calorie diets (VLCDs) find the weight loss to be sudden and quite dramatic. The meal replacements are all nutritionally balanced so you're likely to be getting all the vitamins and minerals you need, albeit not from real food.

Cons:

Initial side effects can include bad breath, a dry mouth, tiredness, dizziness, insomnia, nausea and constipation from cutting down on carbs and fibre. The hardest part of the plan is sticking to it. Giving up normal meals and swapping them for a snack bar or a shake can be boring and feel socially isolating. This isn’t a plan you can stick to in the long term.

BDA verdict:

You need to like the meal replacement products to stay with the plan. Rapid weight loss can be motivating but it is unsustainable. A VLCD that involves eating 1,000 calories a day or fewer should not be followed for more than 12 continuous weeks. If you are eating fewer than 600 calories a day, you should have medical supervision.