Raising livestock (牲畜) is a big part of the carbon emission from agriculture. But it is hard to change people’s habits and get them to give up their hamburgers, especially since more than one-third of Americans eat fast food every day. We previously called for carbon labels on everything from buildings to burgers. Now, a new study from the Johns Hopkins Bloomberg School of Public Health found that labels on fast food affected people's choices.

The study said shifting current dietary patterns to more sustainable diets with less red meat could reduce food-related greenhouse gas emissions by 55% and have health benefits.

The 5,000 participants in the study were shown fake menus. One group got menus with high climate impact labels on red meat items and another had low climate impact labels on fish or plant-based burgers. Both menus were effective in reducing the orders for red meat. But interestingly, the high-impact labels were far more effective, with 23% of the participants choosing a more environmentally sustainable selection, while menus listing low-impact choices encouraged only 10% participants to change.

“We found that labeling red meat items with high-climate impact labels was more effective in increasing sustainable selections than labeling non-red meat items with low-climate impact labels,” wrote the authors of the study.

Lead author, Julia Wolfson, said, “These results suggest that menu labeling, particularly labels warning that an item has high climate impact, can be an effective strategy for encouraging more sustainable food choices in a fast food setting.”

The study points out negative labels might be unpopular: “It is unlikely that the industry would voluntarily adopt a negative label approach; such an approach needs to be carried out via law.   However, high climate impact labels may easily be adopted in settings like universities and hospitals.”

They have a point that this label is aggressively negative, more like a cigarette warning than a food label. In the study, the authors note that future research should test more label designs using qualitative and quantitative research on how people understand different climate impact labels.

It is very likely that you eat three meals a day. Modern life is designed around this way of eating. However, is this the healthiest way to eat? Before considering how frequently we should eat, scientists urge us to consider when we shouldn’t.

Intermittent fasting (间歇性断食), where you restrict your food intake to an eight-hour window, has become a popular area of research. “It allows our digestive system to rest,” says Emily Manoogian at the Salk Institute for Biological Studies. Rozalyn Anderson at the University of Wisconsin explains, “Fasting puts the body in a different state, where it’s more ready to clear misfolded proteins.” Misfolded proteins are faulty versions of ordinary proteins, which have been associated with a number of diseases.

But if intermittent fasting is a healthy way to eat, how many meals does this leave room for? Some experts argue that it is best to have one meal a day. Manoogian does not recommend doing this, since it can increase the level of glucose (葡萄糖) in our blood when we are not eating. Keeping blood glucose levels down requires eating more regularly than once a day, as this prevents the body from thinking that it is starving and releasing more glucose when you do eventually eat in response. Instead, she says, two to three meals a day is best — with most of your calories consumed earlier in the day.“ So, your body can use the energy you feed it throughout the day, rather than it being stored in your system as fat.” But eating too early in the morning should be avoided, as this would not give you sufficient time to fast. This does not mean we should skip breakfast altogether, either, but some evidence suggests we should wait an hour or two after waking up before cracking open the eggs.

Is intermittent fasting realistic? Manoogian thinks that it is best not to specify the best time to eat, as this can be difficult for people with responsibilities and irregular time commitments, such as those working night shifts. But whatever changes you make, researchers agree that consistency is crucial.