Researchers tested 45 take-away lunches eaten by pupils from five secondary schools in the city.
More than half exceeded recommended fat and saturated fat levels, and more than a third had too much salt.
A study by Glasgow Centre for Population Health (GCPH) and Glasgow City Council highlighted the "very poor" nutritional quality of takeaway food in comparison to lunches available in schools.
Fiona Crawford, of GCPH, who led the research said: "Sampling officers purchased 45 pre-agreed items and conducted nutritional analysis of each to compare the quality of key nutrients with Scottish nutrient standards for school lunches.
"Given the fact that a number of pupils also bought sugared drinks, crisps, and confectionery, it is likely that their lunchtime energy, fat and salt consumption will be even greater than that revealed by the nutritional analysis."