Dr Nick Fuller
Leading Obesity Expert at the University of Sydney and founder of Interval Weight Loss.
Losing weight is not just about cutting calories but also finding a program that actually works for the long haul. With so many options out there, it’s easy to wonder: which one delivers the best results?
Interval Weight Loss (IWL), CSIRO, and Weight Watchers all take different approaches to weight management, but how do they compare when it comes to real success? A recent Australian study put them to the test, and the results reveal which program leads the pack.
Let us take a closer look at how they stack up.
Interval Weight Loss (IWL) is a long-term weight management approach designed to stop the cycle of yo-yo dieting. The idea is simple: instead of constantly trying to lose weight, IWL encourages losing weight in small phases and then maintaining it for a set period before continuing. This helps reset your body’s ‘set point,’ making weight loss sustainable rather than a short-term fix. The program also focuses on whole foods, mindful eating, regular movement, and quality sleep—all backed by science to support long-term success.
Want to learn more? Dive into the six key principles of IWL for a deeper understanding.
IWL is a great fit for people who:
Have tried quick-fix diets but struggle to keep the weight off.
Want a structured yet flexible approach to weight loss.
Prefer evidence-based strategies over fad diets.
Are looking for a realistic, long-term plan rather than rapid weight loss.
Need a plan that can be tailored to individual needs, such as medical conditions (e.g., coeliac disease).
IWL might not be the best choice if you:
Want rapid weight loss—this program focuses on gradual, sustainable change.
Prefer a rigid meal plan rather than flexible food choices.
Aren’t interested in tracking habits like sleep, exercise, and eating patterns.
Customisable approach – The IWL PLUS plan allows for personalisation based on medical conditions and dietary needs, such as coeliac disease.
Sustainable results – Helps prevent rebound weight gain by gradually adjusting your body’s set point.
No extreme restrictions – Encourages a balanced approach rather than cutting out entire food groups.
Backed by science – Developed using research on metabolism and long-term weight loss.
Focuses on overall health – Emphasises sleep, movement, and mindset alongside diet.
Takes time – Results aren’t instant, so patience is key.
Requires consistency – Success depends on following the program’s phases.
Less structured meal planning – Some may prefer a program with more specific meal guidelines.
The Commonwealth Scientific and Industrial Research Organisation (CSIRO) Total Wellbeing Diet is a high-protein, low-GI eating plan developed by Australia’s national science agency. It’s designed to help people lose weight while improving overall health, focusing on lean proteins, whole grains, and plenty of vegetables to keep you full and energised.
Unlike extreme low-carb diets, CSIRO takes a balanced approach and allows a variety of foods while keeping protein intake high to support muscle mass and metabolism. The program also includes habit tracking, meal plans, and behavioural coaching to reinforce healthy long-term habits.
This diet is ideal for those who:
Prefer a structured meal plan with clear guidelines.
Like the idea of a high-protein diet to stay full longer.
Want science-backed weight loss strategies rather than fad diets.
Are looking for a program with tracking tools and support.
CSIRO might not be the best fit if you:
Prefer more flexibility in food choices rather than a set meal plan.
Don’t enjoy tracking meals and following strict guidelines.
Have dietary restrictions that make high-protein eating difficult (e.g., vegetarian or vegan diets).
Are looking for a more intuitive, relaxed approach to weight loss.
Structured and science-backed – A clear, well-researched plan with proven results.
High-protein approach – Helps with satiety and muscle maintenance.
Support tools included – Offers tracking, meal planning, and coaching to keep you on track.
Encourages overall health – Focuses on long-term wellbeing, not just weight loss.
Less flexibility – Meal plans can feel restrictive for some.
Requires meal prep – Cooking and planning ahead are key to sticking with the program.
Not ideal for all diets – Can be challenging for vegetarians, vegans, or those with certain dietary needs.
Subscription-based – Some features, like coaching and tracking tools, require paid access.
Weight Watchers (WW) is a flexible, points-based weight loss program that focuses on mindful eating, portion control, and overall lifestyle changes. The core idea is that each food is assigned a point value, which helps you track your intake while still enjoying the foods you love. The program doesn’t restrict certain foods, but instead, it encourages balance by making healthier choices easier to track and maintain.
WW also offers personal coaching, online tools, and community support to keep you motivated. It is ideal for people who prefer a more guided yet flexible approach to weight loss.
The WW program is great for people who:
Want flexibility in their food choices and prefer not to follow rigid meal plans.
Are looking for supportive community and guidance throughout their weight loss journey.
Like the idea of tracking their food and staying accountable without feeling deprived.
Are after a long-term lifestyle change rather than a quick fix.
Weight Watchers may not be the right choice if you:
Prefer a more structured plan with clear, detailed meal guidelines.
Aren’t comfortable with tracking points and counting calories regularly.
Need a highly personalised approach that addresses specific health conditions.
Are looking for a quick, dramatic weight loss solution rather than gradual change.
Flexibility – Allows you to eat a variety of foods without strict limitations.
Supportive community – Group meetings and online tools keep you connected and motivated.
Proven track record – Well-researched program with decades of success stories.
Focus on long-term lifestyle changes – Emphasises building sustainable habits.
Tracking required – Points tracking can be time-consuming for some.
Cost – Premium features and coaching can come with additional fees.
Not a quick fix – Results may take time, which might not suit those seeking fast weight loss.
Can feel restrictive – While flexible, some may still find the constant tracking limiting over time.
New research from the University of Wollongong (UOW) put these three popular weight loss programs to the test, tracking 10,000 people for over a year in a real-world setting. This Australian study compared scientifically backed diets, and IWL came out on top.
IWL led the pack. Of the participants who remained in the program for at least 365 days, 25.4% reached their goal weight. Additionally, 17.6% lost 10% of their body weight, while 62% achieved a minimum of 5% weight loss. These results suggest that IWL’s structured approach supports long-term weight management better than the others.
The CSIRO Total Wellbeing Diet followed closely behind, with 15.4% of participants hitting a 10% weight loss and 48.9% reaching 5%. While still an effective option, it didn’t match IWL’s success rates.
Weight Watchers (WW) ranked third in the study, with 14.4% of participants achieving a 10% weight loss. While it remains a popular program, its results didn’t quite measure up to IWL or CSIRO.
Choosing the right weight loss program is a personal decision. It’s all about finding what works best for your unique needs and lifestyle. So, how do you know which one is right for you?
First, think about what you want to achieve. Are you looking for gradual, sustainable weight loss, or do you want faster results? If your goal is long-term weight management, a program like Interval Weight Loss (IWL) might be a good fit since it focuses on sustainable changes. For those seeking a structured, high-protein approach, the CSIRO diet may align with your goals. If flexibility and a community-driven approach are more important, Weight Watchers could be the ideal choice.
Your food preferences can make a big difference in how well a program works for you. If you’re a fan of high-protein meals, CSIRO is designed to keep you feeling fuller for longer with lean protein and whole grains. For those who want more flexibility in food choices and like the idea of portion control without cutting out entire food groups, Weight Watchers offers the freedom to eat what you enjoy while staying on track. If you prefer an intermittent eating plan that includes whole foods, IWL could be a better fit.
Consider your daily habits and how much time you can dedicate to meal prep and exercise. If you’re someone who needs a structured, easy-to-follow meal plan and enjoys regular coaching and tracking tools, CSIRO and Weight Watchers offer strong support. For those looking for a more flexible, low-maintenance plan, IWL could fit into your routine with minimal hassle, allowing you to focus on gradual lifestyle shifts.
If you have specific health conditions, it’s essential to choose a program that suits your needs. For example, CSIRO’s high-protein approach might not be suitable for those with kidney issues. Weight Watchers offers a more general approach, but if you have dietary restrictions or need a tailored plan due to health concerns, consider consulting with a healthcare professional before choosing a program. IWL, being more flexible, can be adapted to most people’s needs, but it’s important to ensure the intermittent eating style works for your body.
Cost is often a deciding factor when choosing a weight loss program. Weight Watchers offers a range of subscription options, including free and paid plans. While CSIRO provides a comprehensive program, it requires a purchase of books, subscriptions, or meal plans for full access. IWL is a more affordable option, focusing on self-guided changes, which makes it easier on your wallet without compromising effectiveness.
When it comes to effectiveness, Interval Weight Loss (IWL) stands out in comparison to CSIRO and Weight Watchers. The recent study showed that IWL participants had the highest success rate for achieving significant weight loss, with 62% losing at least 5%. While CSIRO and Weight Watchers also produced positive results, IWL proved to be more effective in a real-world setting.
Ultimately, the best program for you depends on your personal goals and preferences, but if sustained, gradual weight loss is your aim, IWL may offer the most effective and practical solution.
Dr Nick Fuller is the founder of Interval Weight Loss and is a leading obesity expert at the University of Sydney with a Ph.D. in Obesity Treatment. Dr Fuller is also the author of three best-selling books and his work been published in top ranked journals in the medical field, including JAMA, Lancet and American Journal of Clinical Nutrition.