Non-Diet Nutrition: Examining the Evidence

This article, which was published in the October edition of NHD magazine, was peer-reviewed by Laura Thomas (PhD, RNutr). Laura is a Registered Nutritionist who specializes in non-diet nutrition and intuitive eating. She also hosts the popular ‘Don’t Salt My Game’ podcast and runs regular online courses for both health professionals and non-professionals about intuitive eating.


 

This article will explore the evidence-base related to non-diet nutrition; which is gaining popularity both in the media and among health professionals. 

Background:

Modern culture puts a strong emphasis on dieting in order to achieve an idealised weight. Many people feel that weight defines health status; which is compounded by the fact that traditional nutrition and dietetic practice is also very weight-centric.

Weight can also be associated with personality traits, overall success and happiness; whether that be at a conscious or subconscious level.

Non-diet (ND) nutrition takes the focus away from weight and dieting

Instead, this uses a holistic approach to encourage healthy behaviours and overall well-being.

This approach celebrates weight inclusivity and body positivity.

Therefore, weight is not measured during most ND consultations and weight stigma is opposed.

The ND approach also highlights that dieting is associated with: weight cycling and health problems; including psychological problems, disordered eating and metabolic issues (as discussed below).

Intuitive eating is an important part of the ND approach. This technique uses specific tools to teach clients how to listen and respond to their own hunger and fullness cues, as well as their psychological needs. ‘Gentle nutrition’ is a concept within intuitive eating which encourages clients to nourish their body with satisfying food, without imposing food rules or giving moral superiority to any type of food. For more information about this, check out this post: What is Non-Diet Nutrition?

Non-diet Nutrition and Health Outcomes:

There is contention about whether weight should be viewed as a key marker of health.

Many people feel that there is a clear link between weight and chronic disease. However some scientists feel that more research is needed to establish whether adipose tissue (in isolation) poses a health risk, and to what degree this may affect health1.

Overall Health

A systematic review of ND interventions from 2015 reported no evidence of2:

  • Significant weight gain
  • Worsened blood pressure
  • Worsened cholesterol
  • Worsened blood glucose levels as a result of this approach

Two studies in this review also demonstrated larger improvements in biochemistry as a result of the ND approach2.

A more recent Canadian study implemented a healthy lifestyle intervention that was aligned with Health at Every Size (HAES)3. This found a significant increase in intuitive eating, as well as improvements in overall diet quality as a result of the ND intervention3. However, the researchers highlighted that more studies are needed to investigate the link between intuitive eating and diet quality.

Diabetes

There is some limited evidence from randomised controlled trials that mindful eating may improve the quality of life of adults with type 2 diabetes, as well as self-management of the condition4-5.

Intuitive eating has also been associated with improvements in:

  • HbA1c levels in adolescents with type 1 diabetes6
  • Glycaemic control in women with gestational diabetes (when combined with dietary education and yoga)7
  • Glycaemic control in non-diabetic people8
  • Insulin sensitivity, glycaemic control and improved HbA1c level in those with type 2 diabetes9 

However as this is still a relatively new concept, more research is needed to see whether intuitive eating is a useful approach on a public health level1.

Mental Health & Eating Disorders

Intuitive eating is associated with improvements in psychological health10.

There is also strong evidence that intuitive eating is beneficial in the treatment of binge eating and binge eating disorder (BED)11-12.

Furthermore, Clifford et al. (2015) found that ND health interventions significantly reduced disordered eating and depression; as well as improving self-esteem levels1.

Intuitive eating may have a role in relapse prevention for some people with anorexia nervosa13. There is also some preliminary evidence that intuitive eating may be useful for inpatient eating disorder recovery14. However more research is needed to investigate this, especially as this can be counter-productive in the acute treatment phase due to the effects of starvation of cognition and the tendency to ruminate at meal times13-14.

Furthermore, Richards et al. (2017) highlight that ”intuitive eating should never be used as the immediate intervention and dietary model for medical stabilization and weight restoration” in those with eating disorders14.

The Effect of Weight Cycling:

There is a common claim that 95% of diets lead to substantial weight regain in the long term; which seems to come from a study in 195915. More recent data has found that only 57% of those who participate in weight loss programmes lose a clinically significant amount of weight (i.e. 5% weight loss)16.

Furthermore, 5 years after weight loss, individuals appear to regain 79% of the weight they initially lost on average17.

It has also been reported that roughly 20-30% of men and 20 – 55% of women have a history of weight cycling18. These high rates of weight cycling may be related to difficulty in adhering to diets in the long term, whereas ND interventions may have higher compliance rates. For example, a 6 month randomised controlled trial found that the drop-out rate of the traditional diet group was 41%, compared to 8% in the ND group19.

Some observational studies have found that weight cycling is associated with an increased risk of mortality, cardiovascular disease and type 2 diabetes18-22. However, overall the supporting evidence is conflicting. A review of this topic from 2014 concluded that “the evidence for an adverse effect of weight cycling appears sparse, if it exists at all”22.

There seems to be a consistent association between weight cycling and an increased risk of BED23-25. 

However, the direction of the this relationship isn’t entirely clear. The association between weight cycling and other psychological issues such as depression is less consistent23-25, but a greater risk of psychological harm has been observed in higher weight people who weight cycle26.

There is also conflicting evidence about whether weight cycling itself makes it more difficult to lose weight on subsequent attempts27-28. Interestingly, some studies have found a higher risk of major weight gain with weight cycling among adolescents, and among those who begin within the ‘normal’ BMI category29-30. There also seem to be an increased risk of cardiovascular disease in those in the ‘normal’ BMI category who weight cycle18.

Weight cycling may be related to homeostatic feedback systems which maintains weight as a certain ‘set point’31.

Part of this feedback system is called ‘metabolic adaptation’, which is a reduction in metabolic rate following weight loss which is bigger than expected (i.e. when when the reduction in body mass is taken into account)32. The longest study which has investigated metabolic adaptation to date was a 6 year study from 2016 which was based on “The Biggest Loser” TV show. This found that following significant weight loss, the participants’ metabolism was approximately 500 calories per day lower than expected33.

It is suggested that this may occur due to changes in adipose tissue or hormonal changes. For example, levels of leptin and insulin drop, and ghrelin levels increase during weight loss, which is associated with increases in appetite and weight regain in lab studies33-35. However, there is not enough evidence to suggest that these changes have a direct impact on weight regain following weight loss in free-living humans35.

The Effect of Weight Stigma:

Studies which associate weight with poor health outcomes often fail to account for the effects of weight stigma.

A recent UK report found that 88% of people in the ‘obese’ weight category reported having been stigmatised, criticised or abused because of their size36.

Feeling discriminated against due to weight has been associated with a significant increase in: physiological stress (measured as allostatic load), metabolic dysregulation, inflammation, depression and disordered eating; as well as a reduction in health behaviours37-39.

In addition, it has been found that experiencing weight stigma during discussions with healthcare professionals can lead to avoidance of healthcare settings40.

Worryingly, weight discrimination has also been associated with increased mortality, even when physical and psychological risk factors were taken into account41.

Conclusion:

The ND approach takes a holistic view of health rather than focusing on diets and weight loss. This approach carries a low risk of harm, especially from a psychological point of view; which is particularly important in view of the evidence that weight stigma can significantly contribute to health problems.

Research is emerging about the beneficial effects of the ND approach. There is currently good evidence for the role of intuitive eating for those with disordered eating patterns and for the treatment and prevention of BED.

However, more research is needed to examine whether the ND approach is also beneficial in other medical contexts and in a public health setting.

Similarly, the effect of weight cycling, increased adipose tissue and the mechanisms related to metabolic adaptation warrant further investigation.


 

For more information about the background to this check out this post: What is Non-Diet Nutrition?

References:

  1. Penney & Kirk (2015) “The Health at Every Size Paradigm and Obesity: Missing Empirical Evidence May Help Push the Reframing Obesity Debate Forward” [available via: https://www.ncbi.nlm.nih.gov/pubmed/25790393]
  2. Clifford et al, (2015) “Impact of Non-Diet Approaches on Attitudes, Behaviors, and Health Outcomes: A Systematic Review” <https://www.jneb.org/article/S1499-4046(14)00796-9/fulltext>  
  3. Carbonneau et al. (2017) “A Health at Every Size intervention improves intuitive eating and diet quality in Canadian women” <http://www.clinicalnutritionjournal.com/article/S0261-5614(16)30140-6/pdf>
  4. Shekhar et al. (2017) “Study the effectiveness of mindful eating on quality of life among adults with type 2 diabetes mellitus in selected hospital of Dehradun, Uttarakhand”. <http://www.indianjournals.com/ijor.aspx?target=ijor:ijone&volume=9&issue=2&article=017>
  5. Miller et al. (2014) “Comparison of a mindful eating intervention to a diabetes self-management intervention among adults with type 2 diabetes: a randomized controlled trial” <https://www.ncbi.nlm.nih.gov/pubmed/23855018>
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