Staying up late doing homework is always tiring. And perhaps when we become tired, we feel the need to eat unhealthy snack food. Recently scientists have been investigating tiredness and snack food.

According to a study in The Journal of Neuroscience, people are more likely to take snacks when they don't get enough sleep.

For the study, researchers from University of Cologne in Germany gave the same dinner to 32 healthy men aged between 19 and 33. Half of the men were then sent home to bed, and the other half were kept awake in the laboratory all night.

The next morning, the participants were asked to consider how much they would be willing to pay for snack food items shown to them in pictures.

According to the researchers, all were similarly hungry in the morning, and had similar levels of most hormones（荷尔蒙）and blood sugar.

However, brain scans showed that when the sleep-deprived（缺少睡眠的）participants looked at the pictures of junk food, they released more of the "hunger hormone". This is the hormone responsible for increasing the appetite, and making us consume more.

Asked about how much they would pay for snacks, "Participants with sleep deprivation were more willing to overspend on food items than those with a good night's sleep," researchers told Science Daily.

Researchers also observed that among the people who hadn't slept, there was greater activity in the part of the brain where food rewards are processed.

The scientists think that sleep-deprived people experience changes to the hunger hormone and the brain's reward system that then leads to a stronger desire to eat snacks with high fat and calories.

"This brings us a little closer to understanding the mechanism（机制）behind how sleep deprivation changes food valuation," Professor Jan Peters, a co-author of the study from the University of Cologne, told The Independent.

Some tips on this:

* Listen to some soft music to relieve your tiredness.

* Do some slight exercise for a short time when you're tired.

* Eat yogurt or fruits to replace snacks with high fat and calories.

* Distance yourself from snacks.

“In high school, I decided to stop eating meat. I love animals. I couldn’t see them suffering.” Babulski says, who is a biologist at Monroe Community College in New York. Teenage Babulski initially lived on starches (淀粉食物) and salads. Eventually she learned to eat a more balanced vegetarian (素食者的) diet. But, Babulski remembers, her mom still wished she’d give up the madness. Mom thought she was going to straight up die.

The decision by Babulski and others to go vegetarian can be threatening to those who view eating animals as typically American. Eating meat is the norm in the United States, even though medical experts have long encouraged people to eat less processed and red meat for health reasons. What is becoming clear is that a meat-heavy diet is also terrible for the planet.

Shifting demand from meat to beans, whole grains, fruits, vegetables and nuts could have many benefits for the climate. A more recent April report from the United Nations Intergovernmental Panel on Climate Change, the IPCC, suggests that the world’s wealthiest individuals could greatly decrease emissions (排放) through lifestyle changes. That’s because households with incomes in the top 10 percent produce roughly 36 to 45 percent of global emissions, while households with incomes in the bottom 50 percent contribute just 13 to 15 percent. Therefore, wealthier individuals, who adopt a low-carbon lifestyle, can help establish new, more sustainable social norms.

Babulski learned about the environmental impacts of meat production. She now shares her personal journey with students in her environmental science course. Many of her students come to realize the power of their individual choices. The little things they do actually do add up and make a difference.

Many facts suggest that children are overweight and the situation is getting worse, according to the doctors. I feel there are a number of reasons for this.

Some people blame the fact that we are surrounded by shops selling unhealthy, fatty foods, such as fried chicken and ice cream, at low prices. This has turned out a whole generation of grown-ups who seldom cook a meal for themselves. If there were fewer of these restaurants, then probably children would buy less take-away food.

There is another argument that blames parents for allowing their children to become overweight. I agree with this, because good eating habits begin early in life, long before children start to visit fast food shops. If children are given fried chicken and chocolate rather than healthy food, or are always allowed to choose what they eat, they will go for sweet and salty foods every time, and this will carry on throughout their lives.

There is a third reason for this situation. Children these days take very little exercise. They do not walk to school. When they get home, they sit in front of the television or their computers and play computer games. Not only is this an unhealthy pastime （消遣）, it also gives them time to eat more unhealthy food. What they need is to go outside and play active games or sports.

The above are the main reasons for this problem, and therefore we have to encourage young people to be more active, as well as steering them away from fast food shops and bad eating habits.