Eating a juicy steak is worse for the environment than frying up some tofu: that should come as no surprise. Going vegan can greatly cut the carbon footprint of your diet. But what about the fewer calories, and lower levels of protein, found in most plant-based foods when compared with meat?

To make the relative carbon impact of foods easier to understand, The Economist proposes a banana index (指数). It compares popular foodstuffs in three aspects—weight, calories and protein—compared to the humble banana, a fruit of middling nutritional value and impact on weather conditions.

Indexing greenhouse-gas emissions to a single food gives a sense of how different foodstuffs rank. Unfortunately for carnivores (食肉动物), beef is bad for the environment no matter how you slice it. Producing one kilogram of mince (馅) causes as many emissions as 109kg of bananas (call it a “banana score” of 109). As for nutritional value, beef’s banana score falls to 54 (one calorie of beef mince causes 54 times as much carbon emissions as one calorie of banana). By protein, it scores seven.

Poultry (家禽) scores 11 bananas by weight and four by calorie. However, as a source of protein, it is more carbon-friendly than bananas: poultry protein emits just three-fifths of the same amount of banana protein. The same applies to salmon. Unsurprisingly, plant-based alternatives to meat do even better: a meat-free burger, for instance, scores just one-fifth of the emissions of bananas per gram of protein.

Our banana index relies on average emissions for a given food. In the real world some producers are more climate-friendly than others, and some foods travel farther to consumers. Our banana index also does not capture other environmental impacts, such as land and water use (though here too, beef tends to perform poorly).

Voting in Europe suggests that most consumers want to be more climate-friendly—and with food production responsible for perhaps a quarter of global emissions, eating with the climate in mind would make a difference. Three-quarters of the respondents said they want labels that would explain the climate impact of their food. In the meantime, our banana index might help.

We all know that eating junk food can make us fat. However, a new study suggests that it can do more than that—it can also make us lazy.

In the study, researchers at the University of California, divided 32 female rats into two groups. The first group was fed a diet of healthy food such as corn and fish, while the second was given a diet of highly processed food rich in sugar, namely “junk food”.

Within three months, the rats in the second group were already much fatter than those on the healthy diet. And when researchers trained the rats to do simple tasks, they found even more differences between the two groups rather than weight.

During the task—pushing a lever (杠杆) to receive a reward of sugar water—the rats on the junk food diet were found to be less willing to move, and they took longer breaks between each push than the lean (瘦的) rats did.

“It is as if the rat is thinking ‘This is too much work’,” Aaron Blaisdell, leader of the study.

But what about the possibility that the fat rats were less passionate about getting sugar water because they were already eating lots of sugar in their daily diet? That’s why researchers repeated the tests by rewarding fat rats with plain water when they were extremely thirsty. However, the results came out just the same.

The experiment didn’t end there. After six months, the rats’ diets were switched, and the overweight rats were given a healthy diet for nine days. However, this change didn’t help reduce their weight or improve their ability to perform tasks, which means the effects of their junk food diet continued. “There’s no quick fix.” said Blaisdell.

For a long time, we’ve believed that people become fat because they are lazy. But this study has proven the opposite to be true as well, which indicates that laziness and obesity (肥胖) are a “vicious cycle (恶性循环)”.

So, if you constantly feel tired, lacking any urge to get up from your chair, it could be that you’ve been studying too hard. But you should also pay attention to your diet.

Eating healthy 100% of the time can seem like a near impossible goal. But along with consistent exercise, healthy eating will make you feel better, give you more energy, and help you perform better in your workouts. 【小题1】.

Here are some tricks to make healthy eating easy:

●【小题2】

Protein is what keeps you full, fuels your muscles, and helps you keep a strong and slim figure. Starting your day out with around 30 grams of protein will not only help get you through the morning without feeling hunger pains, it will also help you get less desires for sugar and carbs(碳水化合物)later in the day.

●Make veggies a main part of every meal

【小题3】. You’ll find that you might actually start to like vegetables, and your body will start to want them because of how good they make you feel after eating them.

●Eat whole foods whenever possible

Simply focus on avoiding processed foods and include as many whole foods as possible in your diet. 【小题4】. But once you discover how food is supposed to taste, eating healthy will become much more natural to you.

●Don’t deny yourself your favorite foods

【小题5】. Because it’ll cause you to feel bitter, more often leading to a binge(大吃)eating session. So if you’re working out and keeping active on a regular basis, allowing yourself a few small treats every once in a while will not only make you happier, it will also make it more likely that you’ll stick with healthy eating in the long run.