Research 2 fad diets and write reports outlining the central claims. Contrast these to the facts and draw conclusions as to the prospects a dieter may face in taking on one of these diets.
The Juice Diet
Claim; Following a juice diet promotes fast weight loss in a short time. It also nourishes every cell in the body and aids detoxification.
Most of the diets under this group promote consuming only juices for a short time. Longer term juice diets permit certain other foods to be consumed alongside the fruit and vegetable juices.
Source; There are many juice diets to follow, a popular programme being the Jason Vale Juice diet for between 3 and 28 days.
Fact; A varied selection of fruit and vegetables provide a great amount of the micronutrients required. However without the fibre content of the fruit and vegetables used only one portion of juice can be counted to your recommended 5 a day. And vitamins A, E and K need fat to be absorbed. On a juice only diet there will be macronutrients that are missing from your daily needs.
Weight loss is common when following a short term juice diet as fat and protein are eliminated and calories are drastically reduced. As you return to a normal diet this weight often returns.
A short term juice diet has some evidence to show that gut health is improved which promotes healthy weight maintenance.
A juice diet is likely to be higher in sugar because the process of juicing frees the sugars (as the fibre is removed) which are then absorbed into the blood more quickly. This can cause more hunger cravings and can have a detrimental affect on the liver. There is a link between drinking juice and tooth decay (British Dental Association).
In regards to detoxing, the body does this continually through the gut, kidneys and liver. These processes will be more effective and the benefits felt but this is an effect of cutting out refined sugars, fats and alcohol rather than a direct benefit of drinking juice.
Prospects; Weight loss will occur due to calorie restriction but this is not sustained loss and weight is quickly gained after the diet period. Due to the extreme and limited variation of the diet, nutrient (micro and macro) deficiency is possible (Vitamin A, E and K – fat soluble, fat, protein). There are short term benefits (3 day juice diet) to increase gut function and promote feelings of well being but there is no evidence of long term benefits.
The Dukan Diet
Claim; Rapid and permanent weight loss without hunger. This is a high protein, low carb diet devised by Pierre Dukan. Dukan was a neurologist but became interested in nutrition and developed (during the 70’s) an eating programme that he released in 2000. The ‘I don’t know how to lose weight’ diet was renamed the Dukan diet when it arrived in the UK market. It is a diet in 4 stages. The first phase restricts the dieter to 72 foods. It is similar to the ketogenic diets as it promotes fat and protein and excludes carbohydrates (including those from fruit and vegetables). This diet makes the body switch from burning glucose for energy to fat therefore promoting weight loss.
The 4 phases are 1. Attack, lasting 5-10 days the dieter can eat 72 high protein foods and 0 carbohydrates. 2. Cruise, lasting until desired weight is reached, pure protein days are encourages but 28 carbohydrates in the form of vegetables are permitted. 3. Consolidation, restricted foods are slowly introduced such as dairy and fruit. Two celebration meals a week are permitted but with some restrictions. 4. Stabilisation, this phase is only permitted if you were able to stay in stage 3 without regaining weight, a weekly protein day is prescribed but other foods are allowed the rest of the time.
Fact; Phase 1 will see weight loss as it is highly restrictive. Once a normal diet is resumed in stage 4 it is very difficult to maintain the desired weight. A survey showed that 80% of people regained the weight they lost over the next 4 years.
This diet is nutritionally unbalanced and excludes fruit, vegetables, fibre, wholegrains. This can lead to symptoms of ketosis (where the body burns fat for energy), fatigue, nutritional deficiencies and weight gain around the waist..
While a high protein, low carb diet has been proven to be effective for weight loss there are no studies to show that the inclusion of the no fat rule work as a diet. One National Institute of health study (Healthline.com) showed that those that ate fat with a high protein, low carb diet burned 69 calories extra per day to those abstaining from fats.
Prospects; Most people will lose weight in the first 2 phases but many put weight back on in the following maintenance phases. It is very restricted so motivation to stick to this diet, particularly maintaining the protein only days, may be difficult to keep up. For some medical conditions (kidney/ liver disease or gout) this may not be a safe diet option. The restrictions see beneficial food groups including some fats to be omitted from the diet leading to nutritional deficiencies.