4.5 stars, rounded up to 5 stars because I want so many people to read it: nutritionists, primary care doctors, people who want to lose weight, people who are prejudiced against people who are overweight, reporters, and many more!
The great: all the research that Guyenet carefully explains. You may have heard snippets of this information before, "Sleep deprivation makes it harder to lose weight!" "Stress increases belly fat!" But reading about it in some depth with all the pieces put together helped me really understand the importance of sleep, feeling in control rather than stressed and helpless, and so much more.
The iffy: Guyenet has been influenced by the paleo folks - when he strays from the research and shares his opinions that becomes clear and it made Guyenet a little less trustworthy for me, although I still thought the book was great. Instead, I wish he would have read about the Blue Zones - the places on earth where people live the longest, healthiest lives - and mused about those lifestyles before writing this book. Also, he is heavily in favor of eating meat (which most people in Blue Zones do- although they eat most of their calories from plants), but when talking about being lean, it seems unbalanced not mention that on average vegetarians are leaner than meat eaters and vegans are leaner still. Not to say I think he should be promoting any particular diet, but since he brought up Paleo, he should look at the big picture.
The main factors that contribute to weight are: genetics plus environment
1. Genetics. It really sucks for those of us who easily gain weight, but it turns out that genetics contribute up to 70% of how much someone weighs. So why didn't we see overweight people at other times in history Because genetics only contribute to weight gain in certain environments - like our current calorie rich environment. (Genetics determines how susceptible we are to the following causes.)
2. How rewarding foods are. Our brain considers foods high in calories to be the most rewarding. When those foods are around, we tend to overeat them because our brain says, "Calories available! Time to EAT!)
3. How valuable foods are. The equation for food value looks something like this: Reward - Effort. We've already learned that high calories equals highly rewarding. The other part of the equation is how hard those foods are to get. To our brains, fast food is very valuable because it's a great deal - very high calorie food with very little effort
Our body wants to keep our weight the same. There are two systems that help it do that:
1. The lipostat which is based primarily in the hypothalamus. The lipostat has one job: to make sure you don't lose any of your valuable life saving, fertility ensuring fat. (This may seem strange to us now, but when we evolved all of these systems, calories were hard to come by so, fat = GOOD, HEALTHY, FERTILE.) The lipostat makes sure your energy systems stay in balance over time. So if you lower your calorie intake, it makes you want to move less and eat more. Ah, gee, thanks, Lipostat. Because of this, often the more weight people lose, the hungrier they get. Until eventually the can't fight their lipostat and their tremendous hunger any longer and they gain all that life saving (from the perspective of the lipostat) fat back, and maybe a little more. Lipostat for the win!
2. We also have a system that "regulates food intake on a meal-to-meal basis by making us feel full and reducing our drive to continue eating after we've had enough." This system is located primarily in the brain stem and gets it's information from the gut.
Recap: two systems that regulate how full you feel: the lipostat which is working to keep your energy intake and expenditure balance the same over time (ie keep the lovely fat on you) and the brain stem which regulates energy intake meal by meal.
This is where your genetics come in. Some people - given a high calorie environment - have a lipostat that says "Ohhhh calories! Let's get a lot of fat on this bod and keep it around. We will be the most fertile in all the land!" While some people's lipostats just say, "Meh. Clearly our genes survived for tens of thousands of years. We'll just keep doing what we been doing and stay lean."
As you can see, most people did evolve to take in more calories when calories are available.
What else influences how much we eat
1. Sleep. When we don't get 7-9 (yes NINE for some people) hours of sleep a night, we eat about 300 calories more than we otherwise would. And remember, our lipostat wants to keep our levels about the same. So, except for the rare genetic freaks (and I say that lovingly), it's not going to want to lose that fat after it's gained it.
2. The threat response system. Guyenet describes this as "stress" and recommends lowering our stress. But in the research he shares, he shows that it's only uncontrollable stress that makes us overeat. I think a clearer way to describe this factor would be: status. In the research he shared, if we have low status and are being criticized and picked on without recourse, we feel stressed and eat more calories than we otherwise would. If we have a lot to do, but we can do it and we feel empowered, then we don't overeat even though we are also feeling "stress."
(Clearly we need an additional word because these are two very different states.)
To sum up so far:
It is how much we eat and how much we move that determines how fat or lean we are. There is not a big genetic difference in how our body processes calories. The big genetic difference is in how much our body wants to weigh. How fat we are is a combination of how much our body wants us to weigh PLUS our food and movement environment.
Can we lower our lipostat
Yes. We just have to roll back the clock a hundred years or so and live like it's 1960 or much earlier, depending on your particular genetics.
1. Eat moderately palatable food. People who were given bland food and lost weight didn't get the starving response that people losing weight on highly palatable food got! This is great news! If it sounds like less fun, it is. But food doesn't have to taste bad, it just has to taste good instead of amazing. Eating whole, natural foods without added sugars, or oils, and very low salt can achieve this. (I've eaten this way for long stretches before and my cravings disappeared and I felt very peaceful, just like the people in one of the studies Guyenet shared.)
2. Exercise. For some people it lowers the weight set point - which again, means you're lipostat won't make you ravenously hungry when you lose some fat. In addition to formal exercise, find ways to move a little all day. Maybe get a treadmill desk or do like the genetically lean folks do and increase your fidgeting. :)
3. As much as you can, don't have high calorie, highly palatable (tasty) foods in your house. Make those foods a lower value by increasing the effort it takes to get to them.
4. Don't look at those foods. Don't have foods out on your counters. Don't watch food commercials on TV. Even seeing these foods can make your brain say, "I see lots of calories! TIME TO FEAST.)
5. Lower inflammation in the brain, so your brain systems that notice you've already eaten are at full capacity. (There is more about this in the book.) You can do this by not eating unhealthy oils or sugar. I wonder if taking an ibuprofen after Thanksgiving would help Or if eating an anti-inflammatory diet would help
6. Maybe don't let yourself get too hungry. When people are hungry, they react to high calorie density food but not to healthier low calorie density food. Could eating more frequently help Or just eating at regular meal times I remember meeting a very slim French woman who said she thought it was ridiculous to eat when you were hungry. "The point of eating at the same time everyday is to eat before you get hungry!" I'm sure there are many best practices, but the main idea is: avoid high calorie density foods when you are super hungry!
What to eat
If you want to be leaner, eat a diet filled with satiating foods, which have these characteristics:
*Low calorie density
*Low to moderate palatability (they taste good but not exciting)