A British Army fitness instructor has suggested the body positivity movement is promoting obesity and making new Army recruits soft.
The serving Queen's Guard has said the movement has led to recruits performing under-par physically and "shying away" from hard graft.
Lance Sergeant Farren Morgan, 36, who works as a physical training instructor for the Coldstream Guards in Westminster, London, insisted youngsters need to stop pretending it is "OK" to be fat.
LSgt Morgan said: "Recruits and candidates influenced by a lifestyle of body positivity lose sight of the importance of consistently maintaining an active and healthy lifestyle which translates into a decline in their physical performance.
"They don't train as often as they should in their spare time, shy away from the high-intensity workouts needed to excel as a soldier, and ultimately struggle to keep up with other soldiers during military drills."
The Army fitness instructor added: "I see it with a lot of people I know in the Army. These young lads – some of them are only 16 or 17.
"I know they watch TV day in and day out. I know from my eight years of training young recruits that their brains are like sponges.
"They see these images in the media, promoting this unhealthy lifestyle – celebrities saying it's OK to eat what you want, as long as you're happy. That misinformation gets stored in their brains and they pass it on."
He went on: "In the media and online, the message received by recruits is significantly different and dangerous. Recruits are seeing people promote an unhealthy lifestyle of 'body positivity' everywhere.
"Body positivity is a lifestyle that promotes complacency and is detrimental to the lives of young soldiers and recruits."
The fitness instructor fears that unhealthy lifestyles could affect decision-making in the field and leave soldiers exhausted.
Lance Sergeant Morgan did highlight that it was just his opinion and that, regardless of the state of the new recruits, the Army has rigorous training and vetting procedures that mean all serving members end up in tip-top condition.
However, he insisted the same could not be said for the British public.
"People always talk about body positivity – being big is OK, and all that sort of stuff. I see that as promoting obesity," he said.
The soldier insisted a culture of instant gratification with takeaway apps was also partly to blame.
He said youngsters need to learn to cook healthier, less calorie-dense meals instead of feasting on unhealthy takeaway pizzas and junk food.
The lance sergeant believes more needs to be done to clamp down on disordered eating and overweight people in the same way that the super-thin look of the '90s has been rightly recognised as unattainable and unhealthy.
He implored people "triggered" by being told to lose weight or seeing calories on menus should "man up and get over it".
"With calories on menus, they were saying that some people with eating disorders might be scared off eating the food if they see how many calories are in it," he said.
"But I think we're scared to just see what's going on and deal with it.
"Just grow a pair. We've been through two world wars, but it seems like we'll try to find anything to moan about."
In a statement, the Army said: "We are aware of a story appearing in a number of media outlets recently concerning health and fitness comments made by a soldier in the Coldstream Guards.
"These articles reflect the opinion of the individual involved, and not that of the chain of command; the British Army were not asked for comment.
"The Army as a D&I compliant organisation must be careful not to stigmatise personnel. The assessments undertaken are based on risk to health and function and not on appearance.
"Army personnel are encouraged and supported to make good health choices."