Three bad sleep habits that make us fat

Three bad sleep habits that make us fat

How we get fat is a hotly debated topic, and it’s certainly worthy of the attention. With 75% of adults in the US being considered overweight, we clearly need new ideas to help slow and reverse this upward trend. Of course, the most relevant variable in controlling our body fat is to control what and how much we eat—this is beyond debate. Though diet is the primary cause, there are other variables that contribute on a secondary level, and one of the biggest is sleep. 

I know, I know—we don’t often blame our sleep habits when we’re fed up with our waistlines. Deficient sleep is obviously known to alter mood and attention [1], but it also increases the risk of serious complications, such as Alzheimer’s disease [2] and heart disease [3]. Lesser known is that too little sleep also contributes to too much fat [4]. 

But before we enter the realm of the metabolic, let’s quickly define good and bad sleep. Good sleep, that which eludes so many of us, is a few things: 1. Falling asleep within 30 minutes of laying down; 2. Only waking once per night; 3. Falling back asleep within 20 minutes, and finally; 4. Waking refreshed and alert. Defining bad sleep is quite simple: it’s not good. Basically, the lack of those four qualities that define good sleep is considered bad sleep. It may be a bit frustrating to think of how many of these you struggle with.

When we don’t sleep well, we set ourselves up for metabolic failure. The first problem is that we get stressed [5]. Now, this won’t be as obvious as the stress you feel with an emergency or when something has gone wrong at home or at work. Stress is defined by an increase in certain hormones, especially cortisol. Cortisol, among its many, many effects, pushes fat cells in the trunk of our body (i.e., around the waist) to get big [6]. Cortisol also makes insulin go up [7], which further amplifies the growth of fat cells all around the body [8]. And it’s not a small impact. A study that explored the metabolic effects of sleep deprivation found that the insulin response to the same breakfast was almost doubled in the “bad sleep” group compared with the “good sleep” group [9]. Even one bad night of sleep can significantly raise cortisol and insulin the next day [10]. 

The second metabolic problem that arises from poor sleep is the temptation we feel to indulge. Bad sleep makes us “snacky”; when we’re tired, we want junk food. It’s difficult to actually measure hunger, but common tools include a “hunger score” (based on a questionnaire) and measuring “hunger hormones” such as ghrelin. Remarkably (and a bit depressing), even one bad night of sleep is enough to more than double hunger and increase ghrelin by ~20% [11]. In this sense, bad sleep is the gift that keeps giving…or rather that jerk that keeps kicking us when we’re down. 

But how does the bad sleep start? Of course, there are countless explanations that are unique to each person, but I believe there are three key culprits that we can address and change to help get our sleep habits back on track:

1. Eating (or drinking) late: Eating food late in the evening has a powerful effect on our sleep. Notice that I’m not saying eating late will make us fat—it won’t necessarily. There’s nothing inherently fattening about eating late, but there is a strong tendency for late-eaters to be weight-gainers [12]. When we snack late in the evening, we go to bed with our intestines busily digesting food and glucose levels spiking. Both of these increase our body temperature, and increased body temperature is a common cause of insomnia [13]. When we eat food, we experience something called the “thermic effect of food”—the body has to work to digest and absorb what we eat, which increases body temperature. With glucose, anytime blood glucose spikes, body temperature follows [14, 15]. Thus, consuming a high-carbohydrate meal before bed gives a boost to glucose and body temperature, resulting in more frequent waking and worse sleep [16].

2. Bad napping: There is a strong link between napping and night-time insomnia—if you nap, you generally sleep poorly. This connection may seem obvious (if not controversial), but the relationship between the two is tricky: Is the napping causing the insomnia or is the insomnia causing the napping? Napping can cause insomnia, especially if it’s after 2pm [17]. Additionally, whether the nap is friend or foe depends on our age. In children and young adults, a nap improves health and brain function; in older adults, the nap is decidedly less helpful, appearing to hurt sleep and increase the overall risk of mortality (i.e., they have a greater chance of dying at any time) [17].

3. Not enough dark: We all know that too much light in the evening can disrupt our sleep. Similarly, too little light in the morning can make it harder to fall asleep later that evening [18]. Some of these consequences have to do with the hormone melatonin—the prototypical “sleep” hormone. While melatonin is certainly well known for its role in sleep, totally overlooked is its effects on fat cells. Melatonin directly stimulates an increase in fat cell metabolic rate [19]. So, if you’re engaging in habits that keep your melatonin low (like too much evening light), you may be directly influencing your fat cells’ propensity to grow or shrink.

Take-away Thoughts

Of course, we should try to improve our sleep habits. Just two good nights of sleep undoes much of the metabolic damage from several nights of poor sleep [20]. Paying attention to the three tips above should help you improve your sleep. And it wouldn’t be an article from a metabolic scientist, unless I shared three additional practical things you can do to help control body fat. 

First, eat early. The adage of “breakfast like a king, lunch like a prince, and dinner like a pauper” may help you control your evening cravings by avoiding a build-up of hunger throughout the day. By eating early, you’ll make it easier to eat less in the evening, allowing you to sleep better. If you practice intermittent fasting, try to end your eating window earlier in the day.

Second, eat smart. By controlling carbohydrates, prioritizing protein, and not fearing fat, you can rest (if not sleep) easy with the knowledge that while the occasional night of bad sleep is working against you, you’re depriving it of its best weapon (i.e., high insulin). Keep insulin low and even if you have higher cortisol from poor sleep, any potential negative metabolic effects will be greatly reduced. 

Third, move more. If you want to rest better at night, move more during the day. Even modest physical activity, like a jog, can lead to a significant improvement in sleep quality in people that normally struggle with sleep [21]. And if you have a choice of when you exercise, go for morning—brief exercise in the morning improves sleep better than comparable exercise in the evening [22].

References

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