Is Fruit Making You Fat? The Facts About Fruit, Fructose and Fat Loss
QUESTION: Tom, I am wondering how many pieces of fruit on a daily basis is acceptable during a fat loss program? I know you've mentioned before that bodybuilders usually minimize all types of sugars for their cut phase and I remember reading something about the liver and fructose that said the liver can only handle so much fructose per day and then the rest gets converted to fat.
My confusion is that I also understand that fruit is overwhelmingly healthy and if I recall correctly, even though fruits have simple sugars (fructose), the other "ingredients" (fiber, etc) prevent you from getting a sugar spike and keep your insulin levels normal. (I think some very sugary fruits, like bananas and grapes, might be a mild exception). As long as I don't add processed sugar to my diet, how many grams of naturally occurring sugar is ok daily? Do I just minimize the amount daily? Thank you.
ANSWER: The fruit and fat loss controversy has been debated for a long time, but this question came up again a lot this past year because of a new study which got some major press, so I'm glad you asked.
First a definition or two. Sugar is any monosaccharide or disaccharide in a food. Sugars occur naturally in foods and sugars are added to foods in a variety of refined and processed forms such as high fructose corn syrup or white table sugar.
Fructose is a naturally-occurring sugar; a monosacharride. Other monosaccharides include glucose and galactose. Lactose, the sugar in milk, is a disaccharide, consisting of glucose and galactose. Sucrose is also a disaccharide, consisting of glucose and fructose paired together (sucrose is 50% fructose).
About 9% of average caloric intake in the United States comes from fructose. For the typical American, only one third of this fructose comes from fruit, while the other two-thirds comes from added refined sugars.
Fructose and glucose have different metabolic effects. Specifically, fructose is an insulin-independent monosaccharide, which means it doesn't stimulate insulin production and it can be stored without the action of insulin. Fructose can also stimulate lipogenesis, but it's important to look at the big picture before you jump to any conclusions about what that means.
In the summer of 2008, a study on fructose and fat from the University of Texas was published in the Journal of Nutrition. It got media attention in the New York Times and across hundreds of websites. The study, "Dietary Sugars stimulate fatty acid synthesis in Adults" said that "acute intake of fructose stimulates lipogenesis." (lipogenesis is the production of fat).
Because of this study and previous ones like it, an argument against fruit in fat loss programs has been made like this:
- Fruit contains fructose
- A study says that fructose turns to fat
- Therefore, if you want to lose fat, don't eat fruit.
Like many areas of fat burning nutrition, it's not quite that simple. To get to the bottom of it, you have to understand how your body metabolizes fructose and you have to look very closely at the designs of these studies.
In the recent study that was interpreted by the media and many readers as "fruit makes you fat," the subjects didn't even eat fruit! They were fed a huge dose of liquid fructose all at once -- 85 grams of carbs with a 75% fructose solution -- for a total of 64 grams of fructose.
What you heard about the liver and fructose is correct. Fructose is not stored in the muscle as glycogen. Muscle does not have the enzymes necessary to synthesize fructose into glycogen in any significant amount. Instead, fructose is rapidly taken up by the liver and is used preferentially to replenish liver glycogen. The liver can store approximately 100 grams of glycogen.
In humans, the liver can handle about 50 grams of fructose daily without stimulating any fat synthesis, so the results of this study are exactly what you would expect. However, 64 grams is not an amount of fructose you're likely to get with whole food such as fruit. On the other hand, you could easily get 50 grams of fructose if you drank a lot of soda or drinks sweetened with high fructose corn syrup.
One big area of confusion in this debate is that many people confuse high fructose corn syrup with naturally-occurring fructose from fruit. High fructose corn syrup (and also sucrose, which is 50% fructose), can provide large amounts of fructose as well as calories, so it's important to make the distinction between fruit fructose and HFCS. HFCS consumption has increased by 1000% just since 1970 and has been attributed as a contributing cause of obesity. HFCS has also been shown to increase one of the hunger hormones, ghrelin.
Another mistake is looking at the total grams of carbs in a piece of fruit and assuming it's all fructose, which is not the case. A typical piece of fruit has approximately 6-7 grams of fructose (maybe 10-12 in a big banana). At that amount, it would take a very large quantity of fruit to experience any conversion of fructose into fat - some say the equivalent of about 5-7 pieces of normal sized fruit.
Keep in mind that the fructose you eat is not necessarily always destined for liver glycogen or conversion to fat. It can also get burned for energy. Also remember that eating too much of anything -- even healthy foods - will slow down fat loss or even cause fat gain. If you eat so much fruit that you're in a caloric surplus, some of it is destined for fat. People who are consistently maintaining a caloric deficit and are highly active have no reason to fear fructose from fruit turning into body fat.
In fact, fruit may actually HELP with fat loss! Most (but not all) fruits are low in energy density, which means they have a low number of calories per unit of volume. This comes from the high fiber and high water content, a combination known to increase satiety - the feeling of fullness after a meal. All fruits contain fiber, and some, such as raspberries, are extremely high in fiber (8.2 grams per cup). Dried fruits, and fruit juice on the other hand are more calorically dense, so they should be kept to a bare minimum on fat loss programs.
Fruit is considered a very healthy food because it contains vitamins, minerals, fiber and numerous compounds with antioxidant properties including vitamins C and E, carotenoids, flavonoids and polyphenols which may protect against free radicals. A study at the University of Navarra in Spain examined the effect of fruit on weight loss and health markers. One group of women was fed a hypocaloric diet (calorie deficit) with 5% fructose from fruit, while a second group was fed a hypocaloric diet with 15% fructose from fruit. There were no differences in weight loss. However, in the group with the higher fruit intake, the LDL (bad) cholesterol decreased and there was less oxidative stress.
A second study from the same University put two groups of women -- a high fruit and a low fruit group - on a hypocaloric diet (600 calorie deficit) for 8 weeks. The weight loss was similar in both groups, but the high fruit group showed improvements in cholesterol levels. The researchers said that the enriched fruit diet may be involved in the favorable effect on cholesterol. On an interesting side note, the higher fruit group retained more lean body mass (adequate liver glycogen levels are a signal to the body of an anabolic state).
There's always a big buzz when these new studies get media coverage, but the fruit and fat loss controversy has actually been going on for decades in the bodybuilding world.
Years ago, there was Dan Duchaine, a famous bodybuilding guru who was one of the first to write in the bodybuilding community about how fructose was handled in the liver. He said that at the level of competitive bodybuilding, removing fruit made a difference. And then there was John Parillo, a bodybuilding trainer from Ohio who for years (and still to this day) tells his bodybuilding clients not to eat fruit.
Like many bodybuilders, I followed their advice and cut out fruit from pre-competition diets in the early days of my career. I got super lean. I later put the fruit back in moderate quantities. I still got super lean. There was no difference in my results either way. But to this day, the bodybuilding community still can't completely shake the stigma that fruit is fattening.
For physique athletes heading down to single digit body fat, every little bit counts, so many bodybuilding and figure competitors still choose to minimize fruit in favor of fibrous vegetables and lean proteins, as an attempt to get every ounce of fat loss possible. However, don't misconstrue that as meaning, "fruit is fattening."
As you might imagine, the idea that fruit consumption should be limited for fat loss also comes up often in the low carb community.
How much fruit you eat may be influenced by whether you've chosen a low carb approach to fat loss. Many low carb dieters and pre-contest bodybuilding, fitness or figure competitors limit the fruit not because they believe it is fattening per se, but because they have chosen a diet plan that restricts the number of total carbs they can eat. With extremely low carb diets, sometimes all the fruit is removed.
For many years, I've preferred, even during restricted carb diets or cutting phases for bodybuilding, to include one or two pieces of fruit. If I were budgeting carbs and calories tightly, I would remove calorie-dense and processed grains and starches before I would remove fruit.
If you're on maintenance level calories, you could easily eat 3-4 pieces of fruit a day and still be well inside your calorie deficit while still allowing room for all the other macronutrients and foods you need. If you're on muscle gain-level calories, or if you're a highly active athlete, you could eat even more.
Consider in closing, these statistics: Between 1970 and 1997, as fitness and health professionals had been imploring people to eat more fruits and vegetables, intake increased by only 19%, providing a mere 2.5 grams per day increase in naturally occurring fructose. In the same time period, HFCS consumption increased by 26% per capita, from 64 g/d to 81 g/day, an average daily intake of 324 calories from added fructose. Just two 12 ounce soft drinks can provide up to 50 grams of fructose or 200 calories. Is whole, fresh fruit really the bad guy?
The bottom line is, fat loss is a matter first and foremost of calories in versus calories out. If you're eating several pieces of fruit while consistently staying in a calorie deficit, you're going to lose body fat, while benefiting, health-wise, from the nutritional value in the fruit. High fructose corn syrup and other added sugars, on the other hand, should be avoided as much as possible.
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