Judith Collins has been blasted as "disrespectful" and "unfair" for saying obesity is "a weakness" that people need to own up to.
Collins said on Tuesday that many Kiwis can do better when it comes to their weight.
"You know what, take some personal responsibility," she told reporters in Wellington.
"We all have to own up to our little weaknesses."
She said people should "not blame systems for personal choices".
Health advocate and obesity specialist Kate Berridge says the comments are "utterly simplistic and totally disrespectful".
"I just had steam coming out of my ears when I heard that," Berridge told Newshub.
"It's absolutely not about personal responsibility - we have a saying that our genes load the gun and the environment pulls the trigger - so it's not just about stepping away from the Tim Tams."
She says Collins' comments come from "pure privilege".
"If you can afford it, you can buy better food, you have access to better education - if you're from a lower socioeconomic background then maybe you've experienced food scarcity, or you haven't had that education. Higher carb content is often cheaper - so it's not just about eat less, move more."
The 2019 New Zealand Health survey found that one in three adults aged above 15 were obese.
Aotearoa has the third-highest rate of obesity in the OECD and it continues to rise, with one in ten children also classed as obese.
But obesity is not just a Kiwi problem - according to the World Health Organization 13 percent of all adults are obese - and the rates have tripled since 1975.
Berridge says the comments from Collins' show a "pretty unfair" view of a global problem.
"It's so much more complex than just 'step away from the pies' - it is going to take policy and attitude changes."
Collins' comments were rejected by Jacinda Ardern, who also called them "simplistic".
"I think if you're so simplistic to call it an issue of collective responsibility then it will never be an issue that we can collectively resolve," she told Newshub.
"I think it's wrong, and if you talk to experts in the sector they would reject [those claims] and so do I."