Why were people so much slimmer in the 70s? Check out photos of your grandmas, moms, and aunties back in the day and you’ll probably wonder this too.
The single reason why people used to be so much thinner than we are today
Let’s get one thing straight. People in the past did NOT burn more calories per day than we do today. I know, surprising right? Yes, in the 70s, folks had to get off the couch to change the television, had to wash dishes by hand, and spent less time sitting down. BUT, it turns out that we burn the same amount of calories as our ancestors even from centuries ago. In general, no matter the time period, women have always and will always burn an average of 1,900 calories a day and men have always and will always burn 2,500 calories a day.
So now that we know that a difference in calories burned is NOT the reason why people were so much slimmer in the 70s, we know that the answer must be a difference in calories consumed. Yes, it’s true that modern Americans consume around 450 more calories each day than did people in the 70s. But, it’s not exactly the difference in the number of calories that’s important—what’s crucial is the difference in type and timing of calories consumed.
Compared to the 1970s, Americans today: 1) eat more foods that cause the hormone insulin to tell our fat cells to store fat and 2) eat more hours of the day, causing the hormone insulin to tell our fat cells to store fat more often.
Trends in Eating Behavior Since the 70s that are making us fat
When comparing American eating habits from the 1970s with the 2010s, the Pew Research Center reports that Americans today eat more flours/grains and less beef and eggs than we did in the past. In the 70s, people ate bacon and eggs for breakfast, but today we eat granola and low-fat yogurt. Although this may sound good, as a professor at Harvard’s School of Public Health, Dr. Ludwig, puts it “Despite eating less fat, we are fatter than ever before”.
When we eat carbohydrates, our bodies release the hormone insulin. Insulin binds to our adipocytes (fat cells) and tells them to store fat. When insulin levels are high, our adipocytes store fat. When insulin levels are low, our muscle cells burn energy. If we want to avoid weight gain, we want to keep our insulin levels relatively low. How do we keep insulin levels low? By avoiding low-quality carbohydrates that cause a spike in insulin levels.
This is why Dr. Ludwig advises us to “opt for natural, unprocessed foods that take time to digest and that deliver energy to the bloodstream in a moderate way instead of in a big rush [to avoid a rush of insulin], the way processed carbohydrates do”. (Harvard).
Another big difference in our eating habits since the 70s is that modern folks snack more often than people in the past. These snacks are often rich in low-quality carbohydrates that cause a spike in blood sugar, and as a result, a spike in insulin.
more eating occasions (snacking) = more insulin = more fat storage
The reason people in the 70s were so much slimmer than we are today is simple—their adipocytes stored less fat by their practice of three key eating behaviors described below.
1970s eating habits you need to adopt TODAY
How have we managed to eat 450 more low-quality, fat-storing calories each day than our parents did growing up?! There are three key differences in how we eat today when compared to folks from the past.
#1 They ate regular meals at regular hours
People in the 1970s ate breakfast early in the morning, lunch in the afternoon and dinner in the early part of the evening. THEY RARELY SNACKED and commonly used the phrase, “don’t spoil your dinner” in order to discourage snacking between lunch and dinner. They didn’t eat anything after finishing dinner at 6pm.
Research shows that people who eat less frequently in a day are less likely to gain weight than people who eat more frequently in a day. Also, people who eat earlier in the day are less likely to gain weight than people who eat later in the day.
#2 They ate food prepared at home
People in the 1970s spent way more time preparing homemade food than we do today. Food eaten at home is known to contain fewer calories and added sugar than food prepared in restaurants. Homemade food is so much more filling than fast food, as it tends to have more fiber and protein than the ultraprocessed junk. For tips based on behavioral science, check out my post on how to cook at home when you have no motivation.
#3 They viewed restaurant food as a treat
People in the 1970s did not normally eat takeout, restaurant or fast food. In fact, many people report only getting to eat out a couple times a year! People in the 70s saw food prepared outside of the home as a special treat. Nowadays however, I know people who order takeout at least once a day. Restaurants and fast food often serve insane portion sizes. When you add regular consumption of snacks to regular consumption of restaurant foods, no wonder we are so much heavier than people from the 70s!