Overweight man exercising

Obesity and dietary sugars

This content has been reviewed by Dr Duane Mellor, Aston Medical School, Aston University, Birmingham, UK.

What is obesity?

Globally, around 1 in 2 adults are living with overweight or obesity (1). 

Obesity is a build-up of excessive body fat, that can lead to an increased risk of developing diseases, such as cardiovascular disease, type 2 diabetes mellitus, and some cancers. Obesity is commonly diagnosed using the body mass index (BMI). BMI measures an individual’s body weight in relation to their height. In adults, it is considered that a BMI greater than or equal to 25 kg/m2 is overweight, and greater than or equal to 30 kg/m2 is obesity (1).

The development of obesity is complex, and no factor is solely responsible. It is the consequence of a wide variety of factors including those related to individual biology, social interactions, eating, physical activity and the environment we live in (2). In simple terms, maintaining a healthy weight requires a balance between calories in (calories taken in from the diet) and calories out (calories used by the body for physical activity and other bodily processes). A calorie (energy) imbalance, whereby excess calories are consumed and not enough are expended, can lead to weight gain over time. However, the exact dynamics of calorie imbalance and changes in body weight is highly complex and can vary from person to person (3).  

Coloured round gummy sweets coated in sugar

Did you know?

Scientific reviews of the evidence, including a review commissioned by the World Health Organization (WHO) (4), have concluded that sugars may be associated with an increase in body weight but this is likely to be due to an increase in calories from increased sugars intake in the included studies, rather than any unique role of sugars per se (4–8). These reviews, including the WHO-commissioned review, do not show harmful effects of sugar when consumed in moderation as part of a diet where calories are not consumed in excess and within recommendations (4–8).

Dietary sugars and risk of obesity

Excess calories (energy) over time from foods and/or beverages, is likely to lead to weight gain. The WHO-commissioned scientific review of the evidence on sugars and body weight concluded that changes in body weight may be explained by the increase or decrease in calorie intake resulting from an increase or decrease in the amount of sugars in the diet (4). However, when calories from sugars are replaced with other sources of calories, leading to a maintenance of total overall calorie intake, there is no change in body weight (4). In other words, this review suggests that sugars intake may only result in weight gain if more calories are consumed than used by the body (4). These reviews, including the WHO-commissioned review, do not show harmful effects of sugar when consumed in moderation as part of a diet where calories are not consumed in excess, and within recommendations (4–8). Ultimately, as the WHO states, "the fundamental cause of obesity and overweight is an energy imbalance between calories consumed and calories expended" (1).

Sugars-sweetened drinks including soft drinks and hot beverages, being held in people's hands. ,

Sugars-sweetened beverages and risk of obesity

When consumption of sugars-sweetened beverages results in excess calories to the diet, the increased sugars-sweetened beverages intake has been associated with weight gain (9). Calories in drinks might not lead to feeling of fullness in the same way that calories in food do, which could result in excessive calorie intake (10). Additionally, in terms of sugars-sweetened beverages, high intakes often occur as part of an ‘unhealthy’ diet and lifestyle, including less physical activity and higher alcohol intake. This could have a role to play in the association between sugars-sweetened beverages and weight gain (11–13).
Balancing on branch

Obesity prevention

Maintaining an energy balance and adopting a healthy dietary pattern, rather than following a specific diet, is the primary strategy for obesity prevention. Reducing high intakes of calorie-dense foods and drinks, which are high in refined carbohydrates and fat, may help with weight loss and maintenance. Systematic reviews of the evidence show that weight loss can occur if overall calorie intakes are reduced (6, 14–16).


  1. World Health Organization. Obesity and overweight. World Health Organization; 2020. https://www.who.int/news-room/fact-sheets/detail/obesity-and-overweight
  2. Butland, B., Jebb, S., Kopelman, P., McPherson, K., Thomas, S., Mardell, J., & Parry, V. Tackling obesities: future choices - project report (2nd edition). Foresight. 2007; 
  3. Hall KD, Sacks G, Chandramohan D, et al. Quantification of the effect of energy imbalance on bodyweight. Lancet. 2011;378(9793):826-837
  4. Te Morenga L, Mallard S, Mann J. Dietary sugars and body weight: systematic review and meta-analyses of randomised controlled trials and cohort studies. BMJ. 2013 Jan 15;346:e7492. 
  5. Choo VL, Ha V, Sievenpiper JL. Sugars and obesity: Is it the sugars or the calories? Nutr Bull. 2015;40(2):88–96. 
  6. Gow ML, Ho M, Burrows TL, Baur LA, Stewart L, Hutchesson MJ, et al. Impact of dietary macronutrient distribution on BMI and cardiometabolic outcomes in overweight and obese children and adolescents: a systematic review. Nutr Rev. 2014 Jul;72(7):453–70.
  7. Fattore E, Botta F, Agostoni C, Bosetti C. Effects of free sugars on blood pressure and lipids: a systematic review and meta-analysis of nutritional isoenergetic intervention trials. Am J Clin Nutr. 2017 Jan;105(1):42–56. 
  8. Chiavaroli L, Cheung A, Ayoub-Charette S, Ahmed A, Lee D, Au-Yeung F, et al. Important food sources of fructose-containing sugars and adiposity: A systematic review and meta-analysis of controlled feeding trials. Am J Clin Nutr. 2023 Apr;117(4):741–65.
  9. Vos MB, Kaar JL, Welsh JA, Van Horn LV, Feig DI, Anderson CAM, et al. Added Sugars and Cardiovascular Disease Risk in Children: A Scientific Statement From the American Heart Association. Circulation. 2017 May 9;135(19):e1017–34. 
  10. Cassady BA, Considine RV, Mattes RD. Beverage consumption, appetite, and energy intake: what did you expect? Am J Clin Nutr. 2012 Mar;95(3):587–93. 
  11. Leme AC, Ferrari G, Fisberg RM, Kovalskys I, Gómez G, Cortes LY, et al. Co-Occurrence and Clustering of Sedentary Behaviors, Diet, Sugar-Sweetened Beverages, and Alcohol Intake among Adolescents and Adults: The Latin American Nutrition and Health Study (ELANS). Nutrients. 2021 May 26;13(6). 
  12. Purohit BM, Dawar A, Bansal K, Nilima, Malhotra S, Mathur VP, et al. Sugar-sweetened beverage consumption and socioeconomic status: A systematic review and meta-analysis. Nutr Health. 2022 Nov 16;2601060221139588. 
  13. Arsenault BJ, Lamarche B, Després JP. Targeting Overconsumption of Sugar-Sweetened Beverages vs. Overall Poor Diet Quality for Cardiometabolic Diseases Risk Prevention: Place Your Bets! Nutrients. 2017 Jun 13;9(6):E600. 
  14. Ambrosini GL, Johns DJ, Northstone K, Emmett PM, Jebb SA. Free Sugars and Total Fat Are Important Characteristics of a Dietary Pattern Associated with Adiposity across Childhood and Adolescence. J Nutr. 2015 Apr 1;146(4):778–84. 
  15. Naude CE, Brand A, Schoonees A, Nguyen KA, Chaplin M, Volmink J. Low-carbohydrate versus balanced-carbohydrate diets for reducing weight and cardiovascular risk. Cochrane Database Syst Rev. 2022 Jan 28;1(1):CD013334.
  16. Ge L, Sadeghirad B, Ball GDC, da Costa BR, Hitchcock CL, Svendrovski A, et al. Comparison of dietary macronutrient patterns of 14 popular named dietary programmes for weight and cardiovascular risk factor reduction in adults: systematic review and network meta-analysis of randomised trials. BMJ. 2020 Apr 1;369:m696.