Naps (小睡) don’t just feel amazing—they are amazing. A study published in the journal Heart found a link between healthy napping and a lowered risk of heart disease. The American Psychological Association (美国心理学协会) points out that naps can improve memory, learning capacity, immune system function and mood.

Sara Mednick, PhD, a cognitive neuroscientist (认知神经学家) at the University of California, Irvine, and author of The Power of the Downstate, explains that when you fall asleep, your body moves through stages that play a role in health.

Stage 1: the “dozing off (打盹儿)” period.

Stage 2: muscles, heart rate and brain activity slow down.

Stage 3: deep, restorative (修复的) sleep.

Stage 4: REM (rapid eye movement) sleep, when brain activity increases and you’re most likely to dream.

Ideal napping times are based around this four-stage cycle.

The 20-minute nap

Between 20 and 30 minutes is one napping sweet spot, according to Mednick, who explains that you get enough Stage 2 sleep to switch your body and mind into full relaxation mode.

The 60-minute nap

Stage 3 sleep is a time for your body to repair tissue (细胞组织), improve the immune (免疫) system and recharge energy stores (储存) . But waking up during this phase can make you feel dizzy (头晕目眩), Mednick says. Most people start to move out of Stage 3 after around 60 minutes, which makes it a good time to set your alarm.

The 90-minute nap

A complete sleep cycle is about an hour and a half, and napping for a full cycle can have big benefits. But naps longer than 90 minutes can interfere (干扰) with nighttime sleep and might even impair memory, according to a study in the Journal of the American Geriatrics Society.

Not a regular napper? That’s OK. “Everyone needs to rest, but not everyone necessarily needs to nap.” says Mednick.

Best Way to Lose Weight-Dieting Tips

How do you eat right to lose weight fast? You’ll discover there are a great number of weight loss diets which promise to help you drop the pounds fast. 【小题1】

Many weight loss diets are aimed at losing weight fast, but aren’t necessarily healthy and won’t create a long-term change for the better. 【小题2】 That means you’ll choose a diet which doesn’t cut out any necessary nutrients (营养物). Most diets suggest that you stop eating fat or carbs (碳水化合物). 【小题3】 You’ll need to make clear of your own body type before making a diet plan. You might also need to try different ways before finding the best way.

If you just need to shake a few pounds off in a short time, your plan won’t be the same as one to lose weight in the long term. The best short-term weight loss plan will be stronger than the best long-term weight loss plan, but both of them shouldn’t get rid of necessary nutrition. 【小题4】 Your body will go into “starvation mode” and your metabolism (新陈代谢) will slow down. As a result your body will keep more weight.

【小题5】 Spread out your meals evenly throughout the day. Any larger meals should be eaten earlier in the day. That gives your body more time and opportunity to burn calories. If you eat a lot before bed, those calories won’t burn but become fat.

Do you think you got enough sleep this past week? Can you recall the last time you woke up without an alarm clock feeling refreshed, not needing caffeine ? 【小题1】. Two-thirds of adults throughout all developed nations fail to obtain the recommended eight hours of nightly sleep.

【小题2】. Routinely, sleeping less than six or seven hours a night destroys your immune system, more than doubling your risk of cancer. Insufficient sleep is a key lifestyle factor determining whether or not you will develop Alzheimer’ s disease. Inadequate sleep, even moderate reductions for just one week, disrupts blood sugar levels so profoundly that you would be classified as pre-diabetic.

Perhaps you have also noticed a desire to eat more when you’re tired? 【小题3】. Too little sleep increases- concentrations of a hormone that makes you feel hungry while stopping a companion hormone that otherwise signals food satisfaction. Despite being full, you still want to eat more. It's a proven recipe for weight gain in sleep-deficient adults and children alike. Worse, 【小题4】, it is in vain, since most of the weight you lose will come from lean body mass(丢脂体重), not fat.

Add the above health consequences up, and a proven link becomes easier to accept: the shorter your sleep, the shorter your life will be. The old maxim “I’ll sleep when I m dead” is therefore unfortunate. Adopt this mindset, and you will be dead sooner and the quality of that (shorter) life will be worse. 【小题5】.