Marc, 44, a father-of-five and a security guard, weighed 17st 1lb at the start of the RTÉ series earlier this month and has lost 11½lb to date.
While he lost 2½lb last week, his weight loss fell short of the 4lb target set for him.
Marc, who has always struggled with his weight, told presenter Kathryn Thomas he was not “overly disappointed” and that it was still early days.
“I feel I can give a lot more,” he said before one of the experts, dietician Aoife Hearne, tore strips off him.
“Marc, I am really annoyed. Honestly, have you stuck to the plan this week?” she asked him.
Marc admitted he had not stuck to the plan and that he was sorry he had the takeaway curry last Saturday.
“Why did I bother coming up with a plan if I felt you could do it better?” Aoife asked him.
Fitness expert Carl Henry was also fuming and told Marc he had never witnessed a reaction like that from any of the leaders.
“This is your third weigh-in. If you don’t care, walk. Go away. I am annoyed at myself for putting you through,” he said.
Marc, from Clane, Co Kildare, is one of the six Operation Transformation leaders chosen from more than 500 people unhappy with their weight who applied for the position.
Last November, when he was one of the 20 finalists, Marc said he wanted to be a leader because he was searching for a balanced, healthy lifestyle. He said he had tried all the diets and his weight had continued to climb.
Karl told Marc bluntly that he did not deserve the chance to change his life at the moment.
Kathryn asked him if he wanted to walk away from the show.
“No. Absolutely not. I’m here to stay,” he said. “I do care. I believe I have the ability to go forward and to make a difference.”
Another leader who failed to reach her target weight loss this week was Jennifer Bonus, from Douglas, Cork. She lost 2½lb but was expected to lose 3lb.
Jennifer, 37, who lives with her daughter, Tara, 12, currently weighs 12st 1lb after losing 8½lb since the series began but has been finding it hard to stick to the eating plan.
Tuesday night’s screening of Operation Transformation had 539,900 viewers.