Systematic reviews and meta-analysis of the data show that the link between a high intake of sugars, and overweight and obesity is mediated by energy intake. The body of evidence continues to grow in this area, with a focus on specific sugars like fructose, and the source of kilojoules, for example sugar sweetened beverages. 

Key research

Barclay AW & Brand-Miller J. (2011). The Australian obesity paradox: A substantial decline in sugars intake over the same time frame that overweight and obesity have increased. Nutrients, 3(4):491-504.
The prevalence of obesity has tripled in Australians since 1980. In Australia, the UK and USA, per capita consumption of refined sucrose decreased by 23%, 10% and 20% respectively from 1980 to 2003. In Australia, there was a reduction in sales of nutritively sweetened beverages from 2002 to 2006 and a reduction in percentage of children consuming sugar-sweetened beverages between 1995 and 2007. The findings confirm an “Australian Paradox”—a substantial decline in refined sugars intake over the same timeframe that obesity has increased. The implication is that efforts to reduce sugar intake may reduce consumption but may not reduce the prevalence of obesity.

Brand-Miller J & Barclay AW. (2017). Declining consumption of added sugars and sugar-sweetened beverages in Australia: a challenge for obesity prevention. Am J Clin Nutr, 105(4):854-863.
In Australia, 4 independent data sets confirmed shorter- and longer-term declines in the availability and intake of added sugars, including those contributed by SSBs. The findings challenge the widespread belief that energy from added sugars or sugars in solution are uniquely linked to the prevalence of obesity.

Te Morenga L, Mallard S & Mann J (2013) Dietary sugars and body weight: systematic review and meta-analyses of randomised controlled trials and cohort studies. BMJ, 345:e7492.
In trials of adults with non-restricted diets, a reduced intake of dietary sugars was associated with a decrease in body weight, while an increased sugars intake was associated with a comparable weight increase. The authors concluded the change in body fatness that occurs with modifying intakes seems to be due to changes in energy intakes, since replacing sugars with other carbohydrates (of equal energy) was not associated with weight change.

Other research

Livingstone KM & McNaughton SA. (2017). Dietary patterns by reduced rank regression are associated with obesity and hypertension in Australian adults. Br J Nutr,117(2):248-259.
Obesity prevalence was inversely associated with low dietary energy density (DED), high fibre and high sugar (natural sugars) diets and positively associated with low-fibre and high sugar (added sugars) diets. Hypertension prevalence was higher on low-fibre and high sodium and saturated fat diets. 

Rippe JM & Angelopoulos TJ. (2016). Sugars, obesity, and cardiovascular disease: results from recent randomized control trials. Eur J Nutr, 55:45-53.
This review of randomised trials, systematic reviews and meta-analyses does not support a link between sugar consumption at normal levels and various adverse metabolic and health effects, including those on energy-regulating hormones, obesity, CVD, diabetes, liver fat accumulation and neurologic responses. 

Rippe JM & Angelopoulos TJ. (2016). Added sugars and risk factors for obesity, diabetes and heart disease. Int J Obes, 40:S22-S27.
The normal added sugars in the human diet (for example, sucrose, high-fructose corn syrup and isoglucose) when consumed within the normal range of normal human consumption or substituted isoenergetically for other carbohydrates, do not appear to cause a unique risk of obesity, diabetes or cardiovascular disease.

Khan TA & Sievenpiper JL. (2016). Controversies about sugars: results from systematic reviews and meta-analyses on obesity, cardiometabolic disease and diabetes. Eur J Nutr, 55(Suppl 2):25-43.
The authors conclude sugar content should not be the sole determinant of a healthy diet as there are many other factors in the diet, some providing excess calories while others provide beneficial nutrients. Rather than just focusing on one energy source, we should consider the whole diet for health benefits.

Choo VL, Ha V & Sievenpiper JL. (2015). Sugars and obesity: Is it the sugars or the calories? Nutrition Bulletin, 40(2), 88-96.
Attention needs to remain focused on decreasing overconsumption of all foods associated with overweight and obesity. Sugar‐sweetened beverages and foods are certainly an important place to start but should not draw attention away from the issue of overconsumption in general.

Ahmad R, Mok A, Rangan AM, at al. (2019). Association of free sugar intake with blood pressure and obesity measures in Australian adults. European Journal of Nutrition. Eur J Nutr, 59:651–659.
A higher free sugar intake from beverages was positively associated with BMI, waist circumference and waist-to-height ratio, while free sugar intake from non-beverage sources was inversely associated with these outcomes. Higher free sugar intake from all food source was associated with a reduced risk of high blood pressure.

Wong THT & Louie JCY. (2018). The direct and indirect effect associations of usual free sugar intake on BMI z-scores of Australian children and adolescents. Eur J Clin Nutr, 72:1058–1060.
Free sugar intake was not associated with BMI z-score in this cohort. Instead of focusing on a single energy source in the diet, improving the quality of the whole diet may be a better approach in tackling childhood obesity.

Ambrosini GL, Johns DJ, Northstone K, et al. (2016). Free sugars and total fat are important characteristics of a dietary pattern associated with adiposity across childhood and adolescence. J Nutr, 146(4):778-784.
An energy-dense dietary pattern high in total percentage of energy from total fat and free sugars is associated with greater adiposity in childhood and adolescence.

Prinz P. (2019). The role of dietary sugars in health: molecular composition or just calories? Eur J Clin Nutr, 73:1216–1223.
Current data indicates that dietary sugars are only associated with an increase in obesity when consumed as an excess source of calories, and with that an increase in the risk of diet-related diseases.