By SUSAN CALLAHAN, Associate Editor and Featured Columnist
When I was a child, I was thin as a rail. Breakfast was sometimes warm --- biscuits, sausage and eggs --- and sometimes it was a large bowl of cornflakes and cold milk. Of course, I, like most children in my day, also ran around, biked and played a good part of the day. So, when recently, I read a snippet from a study conducted at Cornell University which found people who eating something warm for breakfast lose more weight, I was surprised.
The study actually found that small changes practiced at least 25 times per month help us to lose weight. One of their recommendations is to eat something warm within an hour of waking up.
There were no details of any experiments conducted that would have backed up this recommendation so we set out to see if there was any independent scientific evidence that hot meals help you to lose weight. Are hot meals processed by our bodies in the same way as cold meals? Which temperature of meals make our bodies expend more energy processing them?
Hot Meals Speed Up Gastric Emptying
Gastric emptying rate is the amount of time it takes for food or drinks to leave your stomach and enter your intestines.
Some studies have found that the temperature of meals affects the rate of gastric emptying.
In 2009, scientists from Japan's Shimane University conducted experiments that showed that hotter meals have faster gastric emptying times than colder meals. In other words, cold foods stay in your stomach longer.
This finding does not support the Cornell advice to eat warm meals for breakfast to lose weight and this is why.
If hot meals make you lose weight, we would expect that they would have slower rates of gastric emptying, for foods that move more slowly from your stomach and into the digestive process would take more energy to break them down, and this extra energy would create a weight loss.
Slower gastric emptying is also linked with an improved insulin response, which helps to maintain steady blood sugar levels. Since increases in blood sugar levels have been linked to increases in appetite, we would expect that slower gastric emptying would be linked with less weight gain.
But there's another way to look at it. It's important not to read too much into the importance of gastric emptying rate to weight loss or weight gain. Some meals which have a proven link to weight loss also happen to have high gastric emptying rates. For example, vegetables leave your stomach within an hour, much faster than a steak which can take hours to break down. But eating steaks makes you gain weight more easily than green vegetables.
The puzzle of why we gain weight is complex to solve. But here is a big clue.
It's Not About the Temperature or When You Eat--It's About What You Eat
Scientists have recently debunked one of the oldest adages about losing weight --- the one that says we should never skip breakfast if we want to weight because breakfast raises our metabolism for the rest of the day.
Scientists from Cornell University in 2013 studied the effects of skipping breakfast on weight loss.
What they found is that people who skip breakfast actually lose more weight than people who eat breakfast, no matter what kind of breakfast they eat.
The two researchers, Dr. David Levitsky and PhD candidate Corey Pacanowski, examined two groups of people, one of which skipped breakfast and the other which ate breakfast. They then monitored what the two groups ate for the rest of the day. Did the people who skipped breakfast end up eating more for lunch because they were hungrier? Did the people who skipped breakfast gain more weight because their metabolism was more sluggish?
The results they found may surprise you. Compared to those who ate breakfast, the people who skipped breakfast ended up eating 408 fewer calories.
Those 408 fewer calories equate to 12,240 fewer calories each month, which equals a weight loss of 3.5 pounds a month, or 42 pounds a year.
Why didn't the people who skipped breakfast "make up" for the calories by eating more at lunch?
It turns out that the mechanism which regulates how much we eat is not as precise as you might think. Our appetites may be bigger at lunch if we skip breakfast but, apparently, not big enough. We arrive at lunch hungrier if we skip breakfast but not so hungry that we eat the caloric equivalent of what we missed at breakfast. Or, as Dr. Levitsky put it "under eating at one meal does not result in over eating at the next".
More recent studies confirm the same results. A 2017 study from Japan's Prefectural University of Kumamoto looked at 20 healthy lean women between the ages of 21 and 25 years old who either ate breakfast or skipped breakfast. Those who skipped breakfast had slightly lower physical activity during the day but they also ended up eating a lot less overall. In this study, those who skipped breakfast ate a slight bit more at lunch (131 calories) but less overall during the day(262 calories).
What these studies on skipping breakfast show is that, whether you eat a warm, meal or a cold meal at breakfast is far less important than whether you eat anything at all. Those who eat anything at all at breakfast tend to gain more weight than those who skip breakfast.
None of This Applies to Children and Diabetics
Studies on the effect of eating breakfast on children have consistently found that children need to eat breakfast.
Children who skip breakfast have a harder time paying attention and have more fat around their abdomen.
Also, people who are diabetic or hypoglycemic need to eat an appropriate breakfast to maintain steady blood sugar levels.