About two-thirds (65%) of adults were classed as being overweight last year, including 29% who are obese, with the data showing little change since 2008.
The 2015 Scottish Health Survey revealed average waist measurements have increased to 98.2cm (38.6in) for men and 89.5cm (35.2in) for women - up respectively from 95.3cm (37.5in) and 86.3cm (33.9in) in 2003.
Over that period, the number of men with a waist larger than 102cm (40.1ins) increased from 28% to 37% while more than half (52%) of women measure more than 88cm (34.6ins), compared to 39% in 2003.
Two-thirds of all women (66%) and nearly three in five men (59%) are at increased risk of disease based on their body mass index (BMI) and waist circumference, according to the 2015 survey.
Meanwhile, 28% of men and 32% of women were classed as being at a “very high risk level” because of their weight, with 3% of males and 4% of females putting an extreme risk on their health.
Interviews were carried out in nearly 3,800 homes across the country for the research, with some 5,000 adults and 1,400 children questioned.
About a fifth (21%) of adults met guidelines for eating five portions of fruit and vegetables a day while 11% did not consume any, showing little change since 2003.
Meanwhile, 12% of children aged between two and 15 had eaten five portions the day before the research was carried out, with 7% of youngsters not having eaten any.
The proportion of children not eating any fruit or vegetables was down from 10% in 2013.
Nearly three-quarters (73%) of boys were found to be a healthy weight in 2015, up from 63% in 2011, while the number of girls in the category was 70%, a proportion which has remained “relatively steady” since 1998.
Just over a quarter (28%) of children were at risk of being overweight in 2015, with 15% of boys and 14% of girls at risk of obesity.
There has been no improvement in the number of adults who are meeting exercise targets, with 63% carrying out either 150 minutes of moderate exercise or 75 minutes of vigorous exercise a week in 2015, a similar level to 2012.
Tory sport spokesman and former Olympic athlete Brian Whittle said: “There is one very clear message from this report - the SNP has failed on health.
“It has been in sole charge of the brief for almost 10 years now and in that time its initiatives, announcements and education programmes have failed.
“It can’t blame anyone else for this. Nicola Sturgeon keeps saying she wants to be judged on her record.”
Liberal Democrat health spokesman Alex Cole-Hamilton said: “The performance of our Olympians and Paralympians should inspire people right across the country to get healthy and these figures suggest that this will not come before time. At the moment, Scotland is losing the battle of the bulge.
“It is not just waistbands that are under huge strain. Increases in the sort of diseases associated with being overweight put huge pressure on NHS services.
“We need to ensure that people are getting all the information they need to take healthy choices.”
Professor Linda Bauld, Cancer Research UK’s cancer prevention expert based at the University of Stirling, voiced her concerns about the “shocking” childhood obesity levels.
Prof Bauld warned: “If left unchecked, obesity will lead to a rising tide in ill-health, including cancers, and become a crippling burden on the NHS.”