All your life you have been told to eat your fruits and vegetables and I am not going to tell you otherwise. I am, however, going to show you that the idea that you can eat all the fruit you want is not necessarily correct.
I am even going to recommend you limit fruit intake if you are overweight.
How Fruit Can Make You Fat
First a little science; fruit contains a high proportion of a sugar called fructose. More specifically, there are two basic kinds of sugar your body can use: fructose and glucose.
You probably have also heard of sucrose known as table sugar (which is broken down by the gut into 50% glucose and 50% fructose).
Here is where this becomes relevant…
Surprising research performed at the University of Texas Southwestern Medical Center revealed that fructose turns to fat much more easily than glucose.
In this study, researchers fed healthy people breakfast drinks containing three different “sugar combinations” over the course of several weeks, followed by a carefully controlled lunch.
In one test, the breakfast drink contained 100% glucose; in the second 50% glucose, 50% fructose (which is what you’d find in ordinary sugar); and in the third, 25% glucose and 75% fructose.
The researchers were interested in two things, both of which are important:
First, they wanted to measure how fast the sugars in the drink turned to fat in the liver.
Second, they wanted to see how the morning sugar-meal influenced how people metabolized foods eaten later in the day (for example, lunch).
The Findings: Fructose Makes Us Fat
The findings were disturbing. First, the researchers found that fructose got “made” into fat more quickly than other sugars.
And secondly, they found that when fructose was eaten with fat (for example in any junk food snack you can name) the fat was much more likely to be stored rather than burned.
“Our study shows for the first time the surprising speed with which humans make body fat from fructose”, said lead researcher Elizabeth Parks, PhD.
“The carbohydrates came into the body as sugars, the liver took the molecules apart like tinker toys, and put them back together to build fats. All this happened within four hours after the fructose drink. As a result, when the next meal was eaten, the lunch fat was more likely to be stored than burned.”
Even more concerning, Dr. Parks noted that the study likely underestimated the fat-building effect of fructose because the study subjects were lean and healthy. In overweight people, the effect may be amplified.
Why Fructose Makes Us Fat
It turns out that glucose can be used by the body immediately for energy when sugar levels are low. If it is not needed for immediate energy it can be converted to glycogen in the liver or muscles.
If the glycogen stores are full… only then does the excess glucose get converted by the liver into body fat.
Fructose, on the other hand, is not used by the muscles to create glycogen… and is not the preferred source of energy. So any excess fructose is far more likely to be turned into fat by the liver.
“It’s a less-controlled movement of fructose through these pathways that causes it to contribute to greater triglyceride synthesis,” Dr. Parks said.
Can We Eat Fruit at All
This is a good question. Some good sources I know say to stay away from fruit 6 days a week. Some, like me, say to just limit your intake to 3 servings a day (but whole fruits only).
However, if you are having weight problems, you may already be insulin resistant… which means you might be very sensitive to fructose.
So you may want to skip the fruit for a couple of weeks while you try to balance your hormones.
RealDose Weight Loss Formula No. 1 helps reduce the absorption of sugars and slows down the liver’s sugar production. Staying off fruit and other simple sugars can help magnify this effect and maximize your weight loss results.
So if you are finding that you are still “stuck”, try reducing your fruit intake gradually and see if this helps. For many people, this can make a huge difference.
And don’t worry; you can still get all the healthy nutrients you need from the other foods you will be eating.
Obviously you want to stay away from processed sugars like high fructose corn syrup. This contains 55% fructose and 45% glucose.
However, certain natural health advocates seem to imply that you are safe with agave nectar and honey.
Be careful… agave can contain as much as 90% fructose and honey can contain up to 70% fructose, so these are definitely not safe bets!
Fruit juices, smoothies, and dried fruits can also be fructose traps. So even though you might think you are being healthy, these are things to stay away from.
When I go to my favorite “juice bar” down the street, I get vegetable juice instead of fruit smoothies and they make me feel vibrant and alert all day.
One last thing, bananas and some other fruits, such as strawberries, become richer in fructose as they ripen and some of the starch is converted to sugar.
How Much Fructose Can We Eat?
There is some debate, but if you are overweight you probably do have some level of insulin resistance… so while in your fast weight loss phase it might be anywhere from 15 to 25 grams a day for six days a week. (This amount will sneak in through the small levels of fructose contained in complex carbohydrates like beans).
Below you will see a chart that shows you the complete sugar profile of some popular fruits, sugars and candies. Please pay attention to the Tot. Met. Fructose (Total Metabolic Fructose) column. This number number combines the direct fructose content with the amount of fructose contained in its sucrose content. Also keep in mind that Glucose, Fructose and Sucrose do not always add up to Total Sugars since there are some other sugars not shown in the chart (such as galactose, lactose and maltose).
Sugar Profile of Fruits, Sugars and Candies
(in Grams of Sugar per 100 Grams)
|Total Sugars||Glucose||Fructose||Sucrose||Tot. Met. Fructose|
|Purple Passion Fruit or Granadilla||11.2||4.0||3.1||3.3||4.8|
|Sucrose (table sugar)||97.0||–||–||97.0||48.5|
|High fructose corn syrup (42%)||71.0||36.9||29.8||–||29.8|
|High fructose corn syrup (55%)||77.0||30.8||42.4||–||42.4|
|High fructose corn syrup (90%)||80.0||7.2||72.0||–||72.0|
|M & M chocolate candy||64.7||–||–||–||–|
|Bit O Honey||42.4||–||–||–||–|
|Caramello Candy Bar||54.2||–||–||–||–|
|Nestles Crunch Candy Bar||52.4||–||–||–||–|
|Nestles 100 Grand Candy Bar||63.5||–||–||–||–|
|Nestles Plain Milk Chocolate Candy Bar||51.0||–||–||–||–|
It’s because of this information that we formulated a fruit-replacement powder called RealReds. This delicious powder has the same nutritional value as six servings of healthy organic fruits… with 6 grams of fiber and only 1 gram of sugar. Because it only contains 35 calories, you are able to save over 300 calories of pure sugar. Click Here to Learn More.
Until next time,
Steve Sisskind, M.D.
Hi, I'm Dr. Steve Sisskind, Chief Medical Officer & Founder at RealDose Nutrition.
As a young physician, I struggled because my patients came to me with serious health issues, but I didn't have the right tools to help them. Medical school taught me how to put "band aids" on their symptoms with drugs and surgery, but not how to address the root causes of their problems.
Years later I discovered a better approach... based on the fundamental idea that the power of nutrition can transform your health and vitality. But there's a lot of confusion... What foods should I eat? Which supplements should I take? What does the science say?
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Parks, E.J. Dietary Sugars Stimulate Fatty Acid Synthesis in Adults. The Journal of Nutrition, 2008 Jun; 138(6): 1039-46.