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  • Writer's pictureSasha Borissenko

EPISODE 2. Genetics loads the gun

Updated: Aug 20

Is there more to the story than ‘calories in, calories out’? Genetics loads the gun explores the physiology around weight gain, the role of genetics, and the globalisation of ultra processed foods.

Release date: Sunday 13 August, 2023

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

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.

“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.”

To read more, see here.

Chewing the Facts - new episodes out every Sunday. Produced with the NZ Herald, with support from NZ On Air.

You can follow the podcast at iHeartRadio, Apple Podcasts, Spotify, or wherever you get your podcasts.


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- Neuropathic manifestations in infants and children as a result of anaphylactic reaction to foods contained in their dietary

- Effects of diets high in sucrose or aspartame on the behaviour and cognitive performance of children

- 'Finish your soup'

- Healthy eating index and obesity

- Fruit and vegetable consumption and mortality from all causes, cardiovascular disease, and cancer: systematic review and dose-response meta-analysis of prospective cohort studies

- The BMI of twins who have been reared apart

- The genetics of obesity: from discovery to biology

- Genetics and obesity

- Why people become overweight

- Fat Science - why diets and exercise don't work

- Daily energy expenditure through the human life course

- The Long road to leptin

- WHO: Sugars and dental caries

- Eating in the absence of hunger and overweight in girls from 5 to 7 y of age

- Advertising Regulation in the 1980s: The Underlying Global Forces

- Gene regulation and cellular metabolism: An essential partnership

- A food secure New Zealand: International Perspectives in Psychology

- Hiding in plain sight: Experiences of food insecurity and rationing in New Zealand

- Nutritionism and the construction of 'poor choices' in families facing food insecurity

- Neuropathic manifestations in infants and children as a result of anaphylactic reaction to foods contained in their diets

- Increases in physical activity result in diminishing increments in daily energy expenditure in mice

- Appraising the brain's energy budget

- Non-exercise activity thermogenesis in human energy homeostasis

- Exercise and obesity

- Measuring energy expenditures in clinical populations: Rewards and challenges.

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