All dietary interventions to treat overweight and obesity work by reducing dietary energy intake to create an energy deficit
Individuals respond differently to various dietary interventions but level of adherence is key to success
Increase in structured exercise is required to control weight (together with dietary energy restriction) and is linked to health improvements
Regular weighing (once weekly) is a simple behavioural modification technique that has been proven to assist with weight management
This page has been written by the Boden Collaboration on Obesity, Nutrition, Exercise and Eating Disorders, University of Sydney; and reviewed by Professor Tim Gill.
The most effective way of limiting the health impact of overweight and obesity in the community is to prevent weight gain and limit the number of people developing these conditions. However, since more than two-thirds of the adult population in Australia is already overweight, significant efforts need to be directed at providing effective weight management services and interventions to people living with obesity.
Modest weight loss (5 to 10%) has been shown to have a profound effect on the risk of developing type 2 diabetes (T2DM) and is also associated with improvement in blood pressure, cardiovascular disease risk (CVD risk), joint pain, mobility, sexual dysfunction, depression and quality of life (see Healthy Weight Guide). Generally, more weight loss leads to greater improvement. Some conditions, such as sleep apnoea and non-alcoholic fatty liver disease may require 10–15% weight loss for a clinical improvement but for others, such as polycystic ovarian syndrome and fertility, there may be benefits with 2–5% weight loss.1 Achieving weight stability in people with an existing weight problem will help prevent deterioration in obesity-related comorbidities over time. For more details see Health benefits of weight loss.
It is clear that no single intervention will be efficacious, appropriate or acceptable for all people with obesity. Treatment should be individually tailored, and clinical care providers should be able to provide a spectrum of clinically proven treatment options in an individual or group setting.
Multicomponent behavioural intervention remains the cornerstone of overweight and obesity treatment and has been shown to result in significant weight loss with health benefits.2 Most guidelines suggest progressively more intensive interventions may be required in those with greater obesity and/or in the presence of comorbidities (see The Australian Obesity Management Algorithm).
Numerous dietary approaches have been trialled to manage overweight and obesity but they all rely on reducing total energy intake. Researchers attempting to define the most effective overall dietary intervention have come to the conclusion that individuals will respond differently to each approach with the key defining feature of success being the level of adherence to each dietary approach.3 The use of a self-recorded food diary allows a qualitative assessment of the diet and can help to advise tailored dietary modifications.4
Energy deficit approach
All dietary interventions to treat overweight and obesity work by reducing the dietary energy intake to create an energy deficit. The simplest dietary approach for weight loss involves estimating the usual energy intake of an individual and recommending a healthy diet of at least 2500kJ (600kcals) less than one’s usual daily intake. This can be achieved through kilojoule (calorie) counting or following meal plans and is the basis of many commercial programs such as Weight Watchers, health applications and government initiatives such as the 8700 campaign.
A number of dietary approaches to weight loss focus on altering the macronutrient content of the diet but their efficacy is more from greater adherence, leading to reduced total energy intake. Ad libitum low-carbohydrate and low-fat diets have both been shown to reduce body weight, with a very low carbohydrate diet showing the best short-term results in trials, possibly as a result of ketone production contributing to stronger appetite inhibition.5 However, long-term weight loss is not affected by macronutrient content and the food groups recommended by the Australian Dietary Guidelines should still be followed for weight management and overall health.
There are a number of commercial products (usually in the form of meals, bars and drinks) available in Australia containing a fixed energy content that can be used to replace one to two meals within the usual diet and thus create an energy deficit. The use of partial meal replacements has been associated with weight loss and improved overall diet quality.6 The convenience and flexibility of partial meal replacements may increase long term adherence, but transition back to normal foods will require appropriate support to ensure appropriate diet composition for weight loss maintenance and health.
Specific diet or meal patterns
Some weight control programs are based around adopting a recommended dietary pattern with no overt focus on energy intake. The most widely studied diet pattern is the Mediterranean Diet, which is based on a high intake of vegetable, legumes, nuts and fruit, moderate meat intake and replaces saturated fat with monounsaturated fats, such as olive oil. Research indicates that this style of eating has a number of metabolic benefits in addition to assisting with weight control.7
Intermittent Energy Restriction
Intermittent Energy Restriction (IER), which involves significantly restricting energy intake on two to three days per week only (often known as the 5:2 diet), and Intermittent Fasting (IF), which involves avoiding food for whole days or for significant periods of the day, are forms of more intensive energy restriction.8 Some people find this eating pattern easier to adhere to and it is associated with comparable weight loss to more traditional diets9 but it is not recommended for children, the elderly and pregnant or lactating women.
VLEDs and other intense dietary programs
Very Low Energy Diets (VLEDs) are defined as hypocaloric diets which provide a maximum of 800kcals (3350kJ) per day and are usually provided in the form of shakes, soups or bars that are designed to contain the full complement of protein and micronutrients.10 They may be appropriate where other dietary and physical activity strategies have been unsuccessful or when weight presents a significant health risk and/or rapid weight loss is required.11 VLED products replace normal foods and are usually prescribed for 12–16 weeks followed by gradual food reintroduction over 2–8 weeks but have been safely adhered to for up to 12 months.11 When used appropriately, VLEDs can achieve weight loss of around 1–2.5 kg a week12 but additional care and follow up using other interventions is required after this treatment to prevent weight regain or to enable continued weight loss. If tolerated, they can be an appealing option due to the reduced burden of food choice, ease of preparation and motivating effect of initial rapid weight loss. They are not suitable for all people (e.g. pregnant and lactating women and the elderly) and in rare cases may be associated with serious side effects so must be supervised by an appropriately trained health professional.11
Physical activity is an integral part of overweight and obesity management. Although very high levels of exercise (over 300 mins/week)13 are required to achieve reductions in body weight, positive changes in visceral and other ectopic fat stores, and improvements in cardiovascular health occur with relatively low levels of regular, moderate-intensity activity (150 mins/week or less).14 The addition of resistance exercise (three sessions/week) leads to improved outcomes and also increases muscle strength.4 Increases in structured exercise together with dietary energy restriction will be required to control weight but physical activity counselling should also include advice on habitual physical activity in everyday life. Exercise prescription must be tailored to the patient’s ability and health status and focus on a safe and gradual increase.15
Behaviour modification strategies
Strategies focusing on modifying behaviours that contributed to developing overweight and obesity have been shown to be an effective treatment and have more sustained outcomes when used either alone or in conjunction with other treatments.16
Most behaviour modification strategies focus on:
- increasing awareness around triggers for problem behaviours
- identifying feelings and beliefs around weight issues
- increasing structure around common weight related behaviours
- providing support that enables change, and
- setting realistic goals for change.
Self-monitoring, by use of diet and activity applications or devices may be helpful. Regular weighing (once weekly) is a simple behavioural modification technique that has been proven to assist with weight management.17 Identifying and eliminating cues for problem behaviours within the home or work environment is also a useful strategy. Additional professional help may be required with other approaches such as cognitive behaviour therapies (CBT) which aim to help a patient modify both their insight and understanding of thoughts and beliefs concerning weight regulation, obesity and its consequences as well as addressing behaviours that require change for successful weight loss and weight loss maintenance.18
Commercial weight loss programs
Many commercial face-to-face or online weight loss programs exist in Australia, but only a few have been independently evaluated. Most of these programs aim to educate and motivate participants to lose weight by promoting a reduced energy intake with balanced eating, increased physical activity and group support. They often include frequent weekly meetings that focus on intensive behavioural therapy and cognitive restructuring. Research has suggested that well developed and delivered programs can be effective in assisting weight loss. A large international trial of Weight Watchers produced a modest weight loss (≥ 2.5 kg) at 12 months that was significantly greater than the comparator of a physician-led behavioural program delivered in primary care although this difference did not persist at a 24 month follow up.19
Importance of ongoing care and long-term follow up
Obesity is a 'chronic relapsing disease process' requiring follow-up and ongoing management to prevent weight regain, monitor disease risks and treat comorbidities.
Obesity management is multidisciplinary by nature and requires the ability to draw on professionals with complementary expertise. Delivering comprehensive treatment to those with obesity represents a major challenge for the Australian health care system and specialist obesity treatment services are required to support primary care.
For information on medication and surgical treatment options for adults with obesity, see Medication and surgery for adults.