Current guidelines stop the promotion of foods that are high in fat, salt and sugar near the slots when children's programmes are being shown.
The UK Association for the Study of Obesity (ASO) wants to see the same rules applying to internet advertising.
Dr Emma Boyland, an obesity specialist who is based at the University of Liverpool, said: "Rules on food advertising on television ensure young people are not bombarded with promotion of foods that contribute to over-consumption.
"Action also needs to be taken to reduce internet food marketing because companies are not living up to their own commitments.
"Industry self-regulation is ineffective and insufficient to tackle this growing issue with product promotions for items that are high in salt, sugar and fat."
The proportion of youngsters in Scotland who are at risk of obesity or are classed as being overweight is increasing.
Government figures recently suggested that almost 17% are at risk of obesity.
The proportion of children classed as overweight rose from 29.1% in 1998 to 30.6% in 2012.
The call for tougher regulation comes at the start of National Obesity Awareness Week.