University of Newcastle researchers say women also eat more unhealthy foods when they move in with a male partner.
Lead author Amelia Lake says men's diet on the other hand, become healthier when they start cohabiting with a female partner and her influence has a long-term positive impact.
They also lose weight during new relationships and the reason for the change in dietary habits, say experts, is that both partners try to please each other during the 'honeymoon period' at the start of a cohabiting relationship, by adjusting their routine to suit their partner and eating food that he or she likes.
However, because the majority of female partners still assume the traditional role of food shopper and cook, women have the strongest long-term influence over the couple's diet and lifestyle.
The report, by Newcastle University's Human Nutrition Research Centre, reviewed the findings of a variety of research projects from the UK, North America and Australia which looked at the eating and lifestyle habits of cohabiting heterosexual couples, including married couples.
Dr Lake, a research fellow and a registered dietitian, says the findings highlight major health issues which couples needed to address as a team early on in the relationship.
The findings support work by Lake which found more men than women found their partner to be a positive influence on their diet, in terms of encouraging them to eat more fruit and vegetables, eating regular meals and taking control of their food shopping and preparation.
Dr Lake says the blame for an unhealthy lifestyle or diet cannot be blamed just on one's partner, as there are many other things that affect what you eat and do.
However, research does show that a partner's influence on lifestyle is considerable and people who are trying to live healthier lives should take this factor into consideration.
The report is published in the health professional publication Complete Nutrition.
The PROFETAS-researchers are arguing for a 'protein transition': we must eat less meat and partly replace our protein requirements with so-called Novel Protein Foods (NPFs). These NPFs are based on plant proteins that are derived from, for example, peas or soya. While we don't all have to adopt a vegetarian diet, a change in production is necessary, and above all, a change in mentality. It is true that in Western countries meat substitutes are increasingly popular, but the consumption of meat remains persistently high. Even in industrializing countries such as China and Brazil, where meat consumption used to be low, meat consumption is rising rapidly. To achieve real change - a transition - this trend must be reversed on a global scale.
Even more advantages
A protein transition has many additional advantages. A conservative estimation by the researchers found that because so much land would become available to cultivate biomass, a quarter of the world's current energy consumption could be sustainably met from this energy source. Moreover, this can be achieved without affecting grasslands (with extensive meat production) and nature areas, such as tropical rainforests.
A protein transition can also help to put a meat industry plagued by animal diseases and crises back on the rails. Approximately one third of the global trade in cattle and meat is currently afflicted by outbreaks of diseases, causing billions of euros damage.
Finally, a protein transition will also have a positive influence on people's health, through the reduction of many meat-related and obesity-related diseases.
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