Popular diets review

We recommend a nutritionally balanced eating pattern consistent with the Eating and Activity Guidelines for New Zealand Adults for good health. We have reviewed 8 popular diets to make sense of some of the different dietary approaches out there.

For people wanting to lose weight

For people wanting to lose weight, we recommend reducing total energy (calorie) intake by reducing intake of foods and drinks that are energy dense and nutrient poor. For example, sugar-sweetened drinks, alcohol, confectionery and fast food.

For any dietary change to be effective

For any dietary change to be effective it needs to be sustainable long-term, which usually means making small changes that fit your lifestyle. Physical activity is an important component of any weight loss plan and can help you achieve your weight loss goal and improve your health too.

Recommended diets

We recommend these 2 diets.

  • Mediterranean diet

    The Mediterranean diet emphasises eating plenty of plant-based foods, such as:

    • vegetables and fruits
    • whole grains
    • legumes, like lentils, split peas, chickpeas and cooked dried beans, for example kidney beans and baked beans, and nuts
    • replacing butter with monounsaturated fats, mainly from olive oil
    • eating a moderate amount of fish, poultry and dairy products, with little or no red meat.

    Pros

    A Mediterranean diet is effective for weight loss when a person follows it for 12 or more months. The diet is consistent with the Eating and Activity Guidelines for New Zealand Adults. Research has shown that the traditional Mediterranean diet reduces the risk of heart disease and stroke, and improves glycaemic (blood sugar) control in people with type 2 diabetes.

    Cons

    None.

    Advice

    Recommended.

  • Dietary Approach to Stop Hypertension diet

    The Dietary Approach to Stop Hypertension (DASH) diet was developed to help treat and prevent high blood pressure (hypertension). The DASH diet emphasises:

    • plenty of vegetables, fruits and low-fat dairy products
    • moderate amounts of whole grains, fish, poultry and nuts.

    It provides a person with a healthy eating pattern that is consistent with the Eating and Activity Guidelines for New Zealand Adults.

    Pros

    The DASH diet is an effective way to lose weight and become healthier at the same time. Studies have shown that the DASH diet:

    • lowers blood pressure
    • improves glycaemic (blood sugar) control
    • lowers the risk of heart disease and cancer.

    Cons

    None.

    Advice

    Recommended.

Get advice from a health professional

It is important to discuss any changes to your diet with your doctor or clinician first. Some weight loss programmes are not suitable if you have a pre-existing condition such as diabetes or are on medication.

We recommend you get advice from your healthcare provider before you start any of these 3 diets.

  • Commercial weight loss programmes

    Commercial weight loss programmes, such as Weight Watchers and Jenny Craig, provide people with eating plans, pre-packaged meals, guidance and support. Programmes typically offer a 1,000 to 1,500 calorie-per-day portion-controlled diet plan that produces weight-loss of about 0.5 to 1 kg per week.  

    Pros

    Research has found that on average commercial weight loss programmes result in greater weight loss than self-directed programmes do. Many provide counselling, peer support and monitoring.

    Cons

    Many commercial weight loss programmes exist, and some are better than others. These programmes cost money. To  make sure they are effective in the long term, people need to continue to make healthy lifestyle choices after they leave the programme.

    Advice

    A commercial weight loss programme may provide a more intensive intervention for a person who wishes to achieve more rapid weight loss. It may also provide a more motivating and sustainable option.

  • Intermittent fasting diets, including the 5-2 diet

    Intermittent fasting is a pattern of eating that involves periods of fasting (restricting your energy intake) and non-fasting. The most common example is the 5-2 diet, in which a person eats normally for 5 days, and then takes in much less energy (usually 500 to 600 calories per day, which is 25% of recommended requirements) on the remaining 2 days of the week. Over time, the diet reduces a person’s total energy intake, which leads to weight loss.

    Pros

    Intermittent fasting diets can be as effective as other energy-restricted diets, and some people may find them easier to stick to.

    Cons

    Possible side effects from 'fasting days' include:

    • hunger
    • low energy levels
    • light-headedness
    • poor mental functioning.

    You still need to make healthy food choices on 'non-fasting' days. There has been little research about the long-term effect of intermittent fasting on a person's weight or health.

    Advice

    The 5-2 diet may be suitable for some people. Talk to your healthcare provider to develop a weight management plan that is best for you. We do not recommend the 5-2 diet for people with insulin-dependent diabetes.

  • Very low calorie diets

    A very low calorie diet (VLCD) is a medically supervised diet in which you eat 800 calories or less a day for a short time (usually 6–12 weeks). It usually involves replacing most of your meals with low-calorie, specially formulated shakes, soups or bars. Health professionals sometimes recommend VLCDs to promote rapid weight loss among adults who are obese (that is, those with a body mass index (BMI) over 30 kg/m2) in special circumstances; for example, in preparation for surgery. Most people who need to lose weight should not use a VLCD.

    Pros

    VLCDs can be effective for weight loss over short periods, under the supervision of a health practitioner.

    Cons

    VLCDs are hard to follow. They can leave you feeling hungry and low on energy. Other side effects can include:

    • hair thinning
    • tiredness
    • dizziness
    • cold intolerance
    • headache
    • constipation
    • diarrhoea.

    Most people tend to put weight they have lost on a VLCD back on soon after coming off the diet as they return to their previous way of eating. VLCDs are not suitable for:

    • pregnant or breastfeeding people
    • children (aged under 16)
    • older people (aged over 65)
    • people with serious medical and psychological conditions.

    Advice

    Not recommended without professional advice.

Diets not recommended

We do not recommend these 3 diets.

  • Detox diets

    Detox diets claim to:

    • rid your body of 'toxins' resulting from poor diet and lifestyle
    • improve your energy levels
    • result in rapid weight loss.

    They often involve expensive supplements, and require you to cut out whole food groups, typically dairy foods. Some eliminate food all together and allow juice only. The concept of detox diets is unscientific. The body has its own built-in mechanisms to remove waste and toxins. Organs such as the skin, gut, liver and kidney continually 'detoxify' the body.

    Pros

    Cutting out or having a break from alcohol, caffeine or junk food and eating more fruits and vegetables and fewer processed foods is good for your health.

    Cons

    Detox diets can be expensive. There is no evidence that they actually remove toxins, and they can be harmful. You may lose weight quickly on a detox diet, but this is likely to be because you are losing water and your carbohydrate store, rather than stored fat. You are likely to regain the weight as soon as you start eating normally again.

    Advice

    Not recommended.

  • Paleo diet

    The Paleo diet is an eating pattern claimed to be based on the diet of our 'hunter-gatherer' ancestors from the Palaeolithic period (around 2.5 million to 10,000 years BC). It consists of:

    • vegetables
    • some fruit, nuts and seeds
    • naturally occurring fats and oils
    • meat
    • eggs
    • seafood.

    While different variations of the Paleo diet exist, the diet usually excludes:

    • dairy products
    • grains
    • legumes
    • processed foods, including processed oils, sugar and salt.

    Pros

    A Paleo diet includes many healthy foods, such as:

    • whole and less processed foods
    • vegetables
    • fruits
    • meat
    • eggs
    • nuts and seeds.

    Cons

    The key concern with the Paleo diet is that it excludes entire food groups that are important to healthy eating patterns, including grains, legumes and dairy products.

    Also, the diet may encourage eating large amounts of meat, which can be expensive, and runs counter to the Ministry of Health’s recommendation to eat no more than 500 g cooked red meat each week.  

    Advice

    Not recommended.

  • Very low-carbohydrate diets

    Some people see very low-carbohydrate (very low-carb) diets as a better way of losing weight than diets that contain more balanced amounts of carbohydrate and fat. However, research shows that it is not the proportion of macronutrients (carbohydrate, fat and proteins) in a diet that affects weight loss but the total energy (calories).

    Pros

    Cutting poor-quality carbohydrates from your diet is good for your health, such as:

    • sugar-rich foods and drinks
    • food made from refined grains, like white bread, cakes, muffins, and biscuits.

    Cons

    Whole-grain and high-fibre grain foods, such as heavy-grain bread and legumes, contain important nutrients, and are good for your health. People can lose weight on very low-carb diets, but they can also do so on other energy-restricted eating plans. Importantly, there is no evidence of the long-term effects or safety of very low-carb diets. The Ministry recommends diets that contain moderate amounts of carbohydrate.

    Advice

    Not recommended.

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