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Episode 2: Genetics Loads the Gun

Updated: Dec 4

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*Editorial note: This article was originally published in the NZ Herald and follows New Zealand English conventions.


Is there more to the story than ‘calories in, calories out’? Episode two of Chewing the Facts explores the physiology of weight gain, the role of genetics, and the globalization of ultra-processed foods.


In 2020, former National Party leader Judith Collins told Newstalk ZB that “people need to start taking some personal responsibility for their weight”.


Unfortunately, it’s not quite that straightforward.


“It can’t simply be explained by the fact that some people choose to go to the gym and others don’t,” explained Otago University neuroendocrine and metabolic professor, Greg Anderson.


“Obviously, some people put on weight because the energy intake exceeds the energy output. That’s the simple answer, but it hasn’t got us anywhere.”


Speaking in the latest episode of Chewing the Facts, Anderson said some people have a greater basal metabolic rate, which is the energy people burn when they are sitting still, sleeping, and breathing, for example.


Studies show food digestion accounts for 8-15 per cent, metabolic rate can account for 60-80 per cent, and physical activity accounts for just 15-30 per cent.


Specific genes inform the way hormones and metabolism are expressed. Genetic influence varies between 25 and 80 per cent of the factors behind how some people gain weight.


Harvard University research suggests more than 400 different genes contribute to weight, affecting appetite, satiety (the feeling of being full), metabolism, food cravings, and body-fat distribution.


“Free will is not the same for every person. So if we think about what the situation was like maybe 500 years ago, there weren’t supermarkets around, so food was often scarce [...] Most of the people that were contributing to our gene pool lived in this pretty lean environment,” he said.


“We’re just driven to eat [biologically]; we’re wired that way, but some more than others because of these genes.”


World Health Organisation nutrition, health, and development director Francesco Branca told Chewing the Facts the change in food systems had failed to feed people in the right way.


Ultra-processed foods did not contribute to a healthy diet and should be consumed very sparingly, he said.


These are products that are appealing, affordable, easily accessible, heavily marketed, have a long shelf-life, and are high in fat, sugar, and salt.


Branca said the long shelf life undermines the nutritional value of the ingredients and the introduction of additives means they have negative elements but also lack positive elements of the food’s original chemistry.


“Food systems have evolved following other objectives - so, food as commodities, food systems as a source of income, but not to address people’s health and nutrition needs.”


Chewing the Facts: produced with the NZ Herald, with support from NZ On Air.


Research and Sources

 
 
 

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