It is amazing that in today’s day and age many weight loss “experts” still subscribe to the notion that a “calories is a calorie”.
This is simply not true and today we are going to examine how this relates to fruit.
Back in the late 1990′s I was heavily into bodybuilding. Now, say what you want about the “sport” but let me tell you that when it comes to losing body fat whilst retaining muscle bodybuilders are simply the best.
Bodybuilders take the information nutritionists and dieticians prescribe to a whole other level. In fact, the best body transformation coaches I have ever met were all bodybuilders at some point in their careers.
One of the first foods to scrutinize on a competition bodybuilder’s diet is fruit. Yes, fruit does contain many healthy vitamins but it also contains something that is not so good depending upon whether you are trying to lose fat or build muscle- fructose.
Fructose is unique and different from regular glucose. According to Dr. Lustig, a Professor of Clinical Pediatrics in the Division of Endocrinology at UC San Francisco, fructose is iso-caloric but not iso-metabolic. This means that consuming 100 calories of fructose has a different metabolic effect from eating 100 calories of glucose.
Once eaten, glucose goes directly into the bloodstream. Fructose, on the other hand, must first be transported to the liver where one of three things can happen- it can be converted to glucose, stored as glycogen or converted and stored as fat. Your liver can convert both glucose and fructose to fat however the conversion to fat from fructose is much more efficient due to the bypassing of a liver enzyme called phosphofructokinase or PFK.
This does not mean that eating a few strawberries will cause your fat cells to burst at the seams- fructose will only undergo this conversion to fat under certain conditions;
1. In order for your body to convert fructose to fat you must be in a calorie surplus. This means that if you are a person who is eating above their calorie threshold and has not depleted their glycogen through diet and exercise, the efficiency by which your body converts fructose to fat is greatly enhanced. As I write this I am thinking of how many times I have witnessed over fat individuals gorge themselves on melons, mangos and peaches thinking that they were doing something “healthy”…
2. If you are a person who exercises regularly and follows a moderate to low carbohydrate diet your glycogen levels are likely low and eating fruit will have no ill effects. The fructose will be converted to glucose and glycogen and used by the body rather than being stored as fat.
Should YOU be eating fruit?
The answer to this question may sound familiar- it depends. If you are a person looking to lose body fat then you need to be eating fewer carbohydrates, eating in a calorie deficit and exercising your whole body 3 times per week. This will result in a depletion of liver glycogen and as such eating a small amount of fruit will not be a detriment to your fat loss efforts. I always recommend that my clients eat mainly small dark berries as these have the highest nutrient density and lowest amount of fructose.
On the other hand, if you are a person whose goal is to gain muscular body weight you need to be eating more calories and carbohydrates and are likely to have sufficient amounts of liver glycogen. In this instance eating fructose may result in greater fat accumulation despite your hard training efforts. This will require that you keep an eye on your nutrition labels as many weight gain products are sweetened with fructose or Agave (which is 90 percent fructose).
Regardless of your goal I always recommend keeping fructose levels relatively low (about 30 grams or less- the equivalent of approximately 3 apples). This should come from whole fruits only and not from processed foods or high fructose corn syrup.
All fruits are not created equal
All fruits contain fructose but some more than others. Fruits such as lemons, limes, tomatoes, coconuts, grapefruits and avocados are the lowest while prunes, figs, raisins and mangos are among the highest. Honey also has a relatively high fructose content.
For a more complete listing of fructose content in foods you can check out this website: http://nutritiondata.self.com/foods-000011000000000000000.html
From a body composition standpoint the answer to whether or not you should be eating fruit is dependent upon what you are trying to achieve. If you are in a fat loss phase then have some fruit but do so in small amounts and stick with those fruits that pack the biggest nutrition punch (small, dark berries for example). If you are in a weight gain phase then leave the fruit alone or better still, cycle your calories and have some fruit on your low calorie days. This is the strategy I use year round- I have some fruit on my low calorie days and stick to other carbohydrate sources on my higher calorie days. This type of calorie cycling works well for me and has helped me to maintain a very low body fat percentage without feeling deprived. I find that I can give up just about any food for a short period of time. This is the strategy I recommend and I am confident that it will work for you too.