Making Weight-Loss Work. Why Diet Adherence Matters More Than the Diet Itself

Alastair Hunt
6 days ago
5 min read

Updated: 4 days ago

When it comes to weight loss, the best intervention in the world won’t work if people can’t stick to it. The World Health Organisation defines adherence as following an agreed recommendation on behaviour - like diet or medication - over time. However, the review shows there is no single agreed-upon definition or measurement for adherence in weight loss research. Terms like ‘adherence’, ‘attrition’, ‘dropout’ and ‘retention’ are used interchangeably, making comparisons difficult.

Despite this inconsistency, the evidence is clear: adherence is essential for achieving and maintaining weight loss. Yet across studies, many interventions lose their impact over time due to poor adherence. Understanding what helps individuals remain committed can ultimately inform better programme design - and better outcomes.

What Predicts Better Adherence?

Some characteristics make people more likely to stick with a programme. These include being older, male, and having a higher level of education. A lower starting weight and greater early weight loss success also predicted better long-term adherence. In contrast, mental health challenges such as depression or anxiety, financial strain and unrealistic expectations were linked to dropping out.

Importantly, while sociodemographic factors like age or gender cannot be changed, their influence highlights the need for more personalised approaches. For example, younger women with high levels of body dissatisfaction might benefit from additional psychological support or group-based interventions.

What Actually Works?

The study examined multiple types of interventions.

Acceptance and Commitment Therapy (ACT), used within physical activity programmes, increased adherence by helping individuals handle discomfort and focus on long-term values rather than immediate hurdles. This is a form of psychotherapy that helps people embrace their thoughts and feelings rather than fighting or feeling guilty for them. Unlike traditional approaches that focus on changing difficult thoughts, ACT encourages individuals to accept these thoughts and commit to actions that align with their personal values.

Diet-focused interventions had stronger results when they incorporated self-monitoring, whether through apps or structured diaries. These tools gave participants immediate feedback, which was both empowering and motivating. Online nutrition programmes offered flexibility and lower dropout rates. Surprisingly, intermittent fasting - a popular trend - did not consistently lead to better adherence, with some participants finding it too restrictive over the long term.

Notably the study did not review GLP1 agonists as the searches only extended to April 2022, before many of the landmark clinical trials and widespread use of semaglutide and tirzepatide for obesity became mainstream.

Behavioural approaches like self-monitoring and financial incentives also stood out. Programmes offering structured tracking of progress, either through digital tools or manual logs, saw significantly better retention. Reward-based systems - particularly those involving financial reimbursement upon reaching goals - were similarly effective, though more research is needed to determine the ideal incentive structure.

The most robust outcomes came from multi-intervention approaches. Programmes that combined dietary guidance, physical activity, behavioural counselling, and technology produced better adherence than single-component strategies. These layered approaches addressed multiple challenges simultaneously, offering comprehensive support.

The DIETFits Trail

This secondary analysis of Stanford University's DIETFITS trial examined whether dietary adherence and dietary quality influenced weight loss among adults following either a healthy low-carbohydrate (HLC) or healthy low-fat (HLF) diet. The HLC diet emphasised reducing net carbohydrate intake - initially to below 20 grams per day - before increasing to a personally sustainable level. It encouraged whole foods, non-starchy vegetables, and minimising added sugars and refined carbohydrates. The HLF diet similarly aimed to reduce total fat intake while focusing on increasing whole grains, legumes, fruits, and vegetables, and reducing processed foods and saturated fats. Importantly, neither diet imposed calorie limits.

Participants were grouped based on how closely they followed their assigned macronutrient targets and how much they improved overall diet quality, measured by the Healthy Eating Index (HEI-2010).

Those who both adhered well and improved diet quality (HQ/HA group) lost the most weight - around 1.1 to 1.15 BMI points more than those with poor adherence and quality. This group also showed significant improvements in blood pressure, and in the HLC group, better glucose and insulin profiles. The findings highlight that combining dietary adherence with higher-quality food choices yields better outcomes than focusing on macronutrients alone. High-quality eating patterns should be prioritised in weight loss strategies.

Practical Recommendations for Improving Adherence

Track Your Progress Use an app, diary or wearable device to log meals, workouts or weight. Monitoring helps maintain motivation and accountability.
Start with Small Wins Early success - like losing a few kilos in the first month - can significantly increase long-term adherence. Aim for realistic, achievable goals.
Consider Online Support Programmes that offer virtual check-ins, feedback, or educational materials tend to keep people more engaged.
Add Accountability Join a group or work with a coach. Supervision and social support are powerful motivators.
Use Behavioural Contracts Write down your goals, actions, and rewards. Making a formal commitment - especially if it includes financial stakes - can strengthen resolve.
Build a Multi-Component Plan Don’t rely on just diet or just exercise. The most successful plans include a mix of strategies tailored to your preferences and lifestyle.

Final Thoughts

This umbrella review underscores a crucial but often overlooked truth in weight management: adherence isn’t just a personal failing or a matter of discipline. It's a complex, multifaceted process influenced by psychological, social, behavioural, and practical factors. The best weight loss interventions aren't necessarily the most intense or restrictive, but those designed to help people stick with them.

Whether you are starting a new programme or supporting others in their journey, the focus should shift from what people are doing to how we can help them keep doing it. With smarter, more supportive strategies- especially those that integrate self-monitoring and multi-level support - we can create more sustainable paths to health and wellbeing.

If your interest is weight loss, healthspan and longevity, to beat chronic illness or to enhance your mental health and well-being, our consultations and programs deliver results that are tailored to your needs.

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Alastair

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