The Truth About Fruit

Fruit is an important part of a healthy diet, but it's not without its downsides. Learn why that is, and how to prevent this food group from working against you.

Written By Jim Stoppani, PhD

Updated September 28, 2023

I often get bashed by dietitians for warning against eating fruit. If they were to look at my Muscle Building Nutrition Rules, Dieting 101, as well as the diet plans for my Featured Workouts, they’d see I generally recommend eating fruit once or twice a day—once before workouts, and again with lunch, an afternoon snack, or even breakfast. And how could I not, with all the nutritional benefits fruit can provide?

Fruit contains unique antioxidants and other phytochemicals that offer numerous health benefits. Most fruit is largely low glycemic, which means that it doesn't spike blood glucose (blood sugar) levels or insulin levels. When you have fruit before a workout, these low-glycemic carbs provide you with long-lasting energy that doesn't interfere with fat burning. Fruit also provides pure glucose, which is fast-digesting. This means that fruit can give you a small but quick energy spike in addition to longer lasting energy, meaning you’ll get the best of both responses instead of fatiguing suddenly halfway through your workout.

That said, I do warn people about eating too much fruit, which many dietitians read critically as warning against eating any fruit. If they only understood biochemistry a little better they would see that my advice is not only smart for fat loss, but for your overall health as well.

The Problem with Fruit Is the Fructose

Fructose is the main reason why fruit is low-glycemic, or what we call slow-digesting. Fruit's fiber content is another reason, of course, as it helps slow overall digestion as well. As I mentioned above, this slower digestion rate is a good thing because it doesn't lead to spikes in blood glucose or insulin. However, the fact that fructose is low-glycemic is precisely why you want to limit how much of it you eat.

Faster-digesting carb sources like dextrose or glucose are transported directly to the bloodstream. These can be particularly helpful post-workout, as they quickly replenish your muscles’ glycogen stores and spike insulin, which helps increase nutrient uptake. (Check out my article To Carb or Not to Carb? for more on post-workout carbs.)

Fructose, however, is not a sugar that the body can use in its original form; it needs to be converted for the body to use it properly. When you eat fruit, the fructose must first go through the liver to be converted into glucose. This process takes time, which is good for keeping blood sugar levels and insulin low. The downside, however, is that it's bad for your body fat levels.

The Connection Between Fruit and Fat Gain

If your liver is already stocked with glycogen—the body’s storage form of glucose—it will convert fructose into fat. You read that correctly: Fructose is readily converted into fat. That said, since your liver glycogen levels are low in the morning, having fruit for breakfast is generally okay and won't encourage fat gain. In fact, as I explain in my Shortcut to Size diet plan, faster-digesting fruits like cantaloupe or watermelon eaten first thing in the day can even help halt the breakdown of muscle that began due to fasting while you were asleep. But if you have it later in the day (not including as a pre-workout carb source), especially if your overall carb intake is high, there's a good chance the fructose from fruit will be converted into fat.

All Carbs Were Not Created Equal

One study from University of California-Davis found that subjects drinking beverages sweetened with fructose for 10 weeks gained significant amounts of visceral fat (the most dangerous kind of fat) and had lower insulin sensitivity, while those drinking glucose-sweetened drinks did not gain visceral fat or experience a reduction in insulin sensitivity. This is one of the main reasons I recommend limiting fruit intake. It's also why I suggest limiting high-fructose corn syrup (HFCS) in your diet.

Although the corn refiners association say it's similar to sugar, HFCS has at least 5% more fructose. It's a small increase, but more fructose is the last thing you want! Of course, many dietitians who warn against HFCS also feel that you can eat large quantities of fruit, as if the fructose in fruit is magically different than the fructose in HFCS. It's actually all the same. Fructose is fructose regardless of the source.

Studies Illustrate the Downsides of Fruit and Fructose

Another problem with fructose is that it literally gums up the inner workings of your cells. Not all fructose goes to the liver – some does get into your bloodstream, where it’s absorbed by other cells, like muscle cells. This interferes with the cells' ability to function properly and can cause numerous health problems. As the UC-Davis study above found, it can reduce insulin sensitivity, which can lead to diabetes and also interfere with muscle growth. Other research shows that a diet rich in fructose can raise blood pressure, and even impact you on the genetic level.

Studies suggest that that fructose actually alters genes in the brain, potentially leading to issues like memory loss, cognitive decline, even depression and other mental disorders. When affected by fructose on the cellular level, communication between nerve cells can be hindered. In one study testing the effects of fructose on the body, UCLA researchers found that rats (which are genetically very similar to humans) developed problems with memory when fed a diet that included fructose.

Interestingly, they also found that by supplementing with DHA – one of the omega-3 fatty acids, and present at full dose in my fish oil product Omega JYM – this damage was mitigated. For more on how DHA can protect your brain from the harmful impacts of fructose, watch the video below. You can also read more on this study in the Highlighting DHA section of my Omega JYM Ingredient Breakdown.

Jim's Take-Home Message

So should you avoid fruit completely? No! I've never recommended that. Check out my Power Foods article to find my breakdown on a number of fruits (and other foods) that you should include in your diet. Just be sure to eat fruit in moderation, and at the right times. The two best times of day to have fruit are when you first wake up in the morning and before workouts.

As for what types of fruit are the best to eat, my advice always starts with APPLES. Here's a video I shot recently discussing the benefits of apples as one of the best pre-workout carb sources you can find:

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