Three quarters of men will be overweight within five years, research shows.
Health messages are often targeted towards women
The Men's Health Forum said a change in the way weight campaigns were aimed at men was needed to avert the crisis.
It said part of the problem was that messages were often targeted at women - despite more men (65%) than women (55%) being overweight or obese.
The group has produced a health guide in the style of a car manual to help change attitudes.
A survey by the forum found many men were against seeking help to lose weight.
More than half of men said they would not go to a GP for advice, while 87% were against joining slimming clubs.
The survey, of 1,028 men aged 16 to 64, revealed men were more likely to be motivated to lose weight to help them "chat someone up" (43%) than for health reasons (39%).
The men surveyed also showed a lack of understanding about the health implications of being overweight.
Only two thirds knew that being overweight was linked to diabetes, while a third were aware of the link to erection problems.
Projections for 2010, based on present trends show that 75% of men will be overweight or obese by 2010, compared to two thirds of women, the forum said.
The new guide, the HGV Man manual, has been produced in conjunction with car manual publishers Haynes.
It delivers a health message in a male-friendly way, referring to seeing a doctor as having an MOT.
Dr Ian Banks, president of the Men's Health Forum and author of HGV Man, said: "Men are often less well informed about nutrition and how to lose weight than women.
"To be effective advice must be tailored to men.
"Currently, health messages about weight loss are most geared to women in ways that men don't connect with.
"Support for male weight loss has to be provided in a range of settings, such as the workplace and online, as well as through the GP practice."
National Obesity Forum chairman Dr David Haslam said men had to pay more attention to their weight.
"Men need to be more aware of the health implication of excess abdominal fat and how to lose weight.
"Reducing waist size alone can lead to significant improvements in health, so being able to notch in a belt can be a good and simple way of gauging healthy weight loss."