As nuts are an energy-dense food, due to the heart-healthy fats they contain, there’s a widespread perception that eating them will cause weight gain.

But decades of research shows this is not true. Nuts are actually linked with a decreased risk of being overweight or obese, and regularly eating nuts reduces body weight, body mass index (BMI) and waist circumference [1,14].

Studies have looked at many different tree nuts. The take out? All nuts have a positive effect on weight, so enjoy a variety every day!

What the research says

A major review of the evidence, published in 2021 in Obesity Reviews, found nut consumption does not lead to increased body fatness (14).

The systematic review and meta-analysis considered the outcomes of six prospective cohort studies and 86 randomised controlled trials (RCTs), involving more than half a million people. Nuts were linked with a 7% lower rate of overweight/obesity in long-term prospective cohorts, and RCTs showed a ‘high certainty’ of no adverse effect of nuts on body weight.

Evidence from another systematic literature review and meta-analysis of three prospective cohort studies and 62 RCTs, published in 2018, found nut consumption was linked with reduced overweight/obesity. And in the RCTs, a diet enriched with nuts reduced body weight (-0.22kg), BMI (-0.16kg/m2) and waist circumference (-0.51cm), compared to control [1].

And as far back as the 1990s, two very large, well-regarded studies – the Adventist Health Study and the Nurses’ Health Study – found significant inverse associations between the frequency of nut consumption and BMI.

Health professionals and dietary guidelines may recommend nuts, for those without allergies, for their cardiometabolic benefits without stipulations or concern of an adverse effect on weight control. (14)

How do nuts help manage weight?

Satiety and reduced appetite: The plant-protein and fibre in nuts help satisfy hunger and reduce appetite [10, 11], and the healthy fats help release satiety hormones – cholecystokinin (CCK) and peptide YY (PYY) – in the gut, which help to tell you when you’re full [2, 3]

Increased resting energy rate: The body’s metabolism increases (by up to 10%) immediately after eating nuts, meaning kilojoules are burnt up.

Not all nut kilojoules are absorbed: The fibrous cell walls in nuts stop our bodies absorbing up to 30% of the kilojoules in nuts [4-6]. This energy is instead excreted. 

Spontaneous dietary adjustments: Research suggests that eating nuts can reduce energy intake at later meals [7]. In fact, studies show that nut consumers eat significantly less kilojoules – by up to as much energy as the nuts provided – at their next meal! [13]. This is likely due to the protein, fibre and healthy fats in nuts.

A serve of nuts is 30g, or about one handful. We should all aim to eat a handful of nuts every day. But there’s no reason why you can’t eat more. Research suggests that around two handfuls (60g) a day helps lower cholesterol [8], and that up to 120g daily can be eaten without gaining weight [1].

References

  1. Li, H., et al., Nut consumption and risk of metabolic syndrome and overweight/obesity: a meta-analysis of prospective cohort studies and randomized trials. Nutr Metab (Lond), 2018. 15: p. 46.
  2. Cassady, B.A., et al., Mastication of almonds: effects of lipid bioaccessibility, appetite, and hormone response. Am J Clin Nutr, 2009. 89(3): p. 794-800.
  3. Pasman, W.J., et al., The effect of Korean pine nut oil on in vitro CCK release, on appetite sensations and on gut hormones in post-menopausal overweight women. Lipids Health Dis, 2008. 7: p. 10.
  4. Mandalari, G., et al., The effects of processing and mastication on almond lipid bioaccessibility using novel methods of in vitro digestion modelling and micro-structural analysis. Br J Nutr, 2014. 112(9): p. 1521-9.
  5. Ellis, P.R., et al., Role of cell walls in the bioaccessibility of lipids in almond seeds. Am J Clin Nutr, 2004. 80(3): p. 604-13.
  6. Novotny, J.A., S.K. Gebauer, and D.J. Baer, Discrepancy between the Atwater factor predicted and empirically measured energy values of almonds in human diets. Am J Clin Nutr, 2012. 96(2): p. 296-301.
  7. Hull, S., et al., A mid-morning snack of almonds generates satiety and appropriate adjustment of subsequent food intake in healthy women. Eur J Nutr, 2015. 54(5): p. 803-10.
  8. Sabate, J., K. Oda, and E. Ros, Nut consumption and blood lipid levels: a pooled analysis of 25 intervention trials. Arch Intern Med, 2010. 170(9): p. 821-7.
  9. Neale, E., et al., The effect of nut consumption on heart health: an updated systematic review of the literature. 2018. Nuts for Life, unpublished.
  10. Noakes, M., The role of protein in weight management. Asia Pac J Clin Nutr, 2008. 17 Suppl 1: p. 169-71.
  11. Pereira, M.A. and D.S. Ludwig, Dietary fiber and body-weight regulation. Observations and mechanisms. Pediatr Clin North Am, 2001. 48(4): p. 969-80.
  12. Mattes, R.D., The energetics of nut consumption. Asia Pac J Clin Nutr, 2008. 17 Suppl 1: p. 337-9.
  13. Tan, S.Y., J. Dhillon, and R.D. Mattes, A review of the effects of nuts on appetite, food intake, metabolism, and body weight. Am J Clin Nutr, 2014. 100 Suppl 1: p. 412s-22s.
  14. Nishi, SK., et al. Are fatty nuts a weighty concern? A systematic review and meta-analysis and dose–response meta-regression of prospective cohorts and randomized controlled trials. Obesity Reviews. 2021; e13330. https://doi.org/10.1111/obr.13330
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