20 October 2025

Back when I was a naturopathy student in the early 1990s, no one whom I was acquainted with would have taken this question seriously. At that time, everybody ‘knew’ that being overweight was due to eating too much fat. End of story.

But then, in the mid-90s, the Atkins diet – which exonerates fat, and vilifies carbohydrates as the culprit in weight gain – was reborn as the best-selling book Dr Atkins’ New Diet Revolution (having died a rapid death in its first incarnation as Dr Atkins’ Diet Revolution in the early 1970s)¹. A wave of me-too books followed: The Zone Diet, Sugar Busters, The South Beach Diet, Protein Power and a swag of others of lesser repute.

The paleo diet craze followed in the wake of the Atkins diet. Walter Voegtlin’s book The Stone Age Diet soft-launched the notion of ‘eating like our ancestors’ back in 1975, but the publication of Loren Cordain’s The Paleo Diet in 2002 finally sent the movement mainstream.

Although the Atkins diet included an induction phase intended to induce temporary ketosis, it wasn’t until the 2010s that books promoting permanent ketosis as a weight loss strategy became popular, spawning the ‘keto diet’ trend. But even this wasn’t hard-core enough for some, and hence the carnivore diet spun off from the ketogenic diet.

Here’s how Google Trends maps the rise and fall in public interest in each of these diet trends:

While the proponents of each of these diet-styles vary on some details, they all sing from the same hymn sheet on one point: ‘carbs’ (carbohydrate-rich foods) are bad. Carbs raise insulin levels, carbs turn to fat, carbs cause diabetes, carbs make your arteries block up with plaque, carbs cause inflammation, and so on ad nauseum.

I’ve meticulously debunked each of these claims in several previous articles, including Ketogenic diets Part 3 – Weight loss and Part 4 – Diabetes, Diving down the low-carb rabbit hole Parts 1 and 2, The truth about diabetes – and why you’re not hearing it and Sweet Poison debunked. The bottom line is this: carbohydrate-rich whole natural foods promote optimal health and weight; carbohydrate-rich ultraprocessed foods undermine health and drive weight gain. Honestly, it’s just not that complicated.

But here we are in 2025, and I’m still being told by clients on their first visit to me, that they’re restricting their fruit intake because their personal trainer, or some book they read, or a blog they follow, or a ‘nutrition influencer’ (cue sound of fingernails scratching down a chalkboard) told them that “fruit is full of sugar” and “fruit makes you fat”.

I used to simply dismiss these preposterous claims with a rhetorical question: “Have you ever seen a fat monkey?”, or if I felt particularly edgy, “How many obese people with shopping trolleys full of fruit do you see in the supermarket?” But the notion that fruit is fattening has wormed its way so deeply into the collective unconscious that I now need to address it more comprehensively in order to loosen its grip on my clients’ minds.

So this is what I tell them:

1. Epidemiological (population-based) studies have consistently found that the more fruit you eat, the slimmer you are

Here is just a small sample of a voluminous body of research on this topic:

• In the Nurses Health and Health Professionals Follow-up Studies (a total of 117,918 participants), each additional daily serving of fruit was associated with a weight loss of 240 g (0.53 lb) over four years, with the greatest weight loss observed in those who were the most overweight to start with (up to 360 g [0.79 lb] per serving, per day, in obese people). Participants who increased their fruit intake over the course of the study were more likely to lose weight than those whose fruit consumption stayed the same or went down.
• The Women’s Health Initiative study drew on data from 49,106 postmenopausal US women, finding that every additional serving per day of whole fruit was independently associated with a loss of 430 g (0.94 lb) over three years of follow-up.
• A systematic review and meta-analysis of prospective cohort studies published in 2015, which included 17 cohort studies and a total of 563,277 participants, found that people who ate the most fruit weighed less, and had a lower waist circumference (an indicator of lower visceral fat deposition), than those who ate the least, and also had a lower risk of gaining weight over time.

Drinking fruit juice has the opposite effect, although the impact is very modest. In the Women’s Health Initiative study, each daily serving of 100 per cent fruit juice was associated with a three-year weight gain of 180 g (0.39 lb) – not enough to give up wearing skinny jeans, but still a cautionary tale.

2. Randomised controlled trials consistently show that adding more fruit to people’s diets leads to weight loss

• In a randomised controlled trial conducted in 411 overweight and obese Brazilian women, adding either three pears or three apples to the daily diet facilitated both weight loss and reduction in blood glucose level.
• To test the hypothesis that high intake of sugars – in particular, fructose – from natural sources induces metabolic syndrome and obesity, 131 overweight and obese Mexican individuals were randomised to either a low-fructose diet (less than 20 g/d) or a moderate-fructose diet (50-70 g/d) in which most of the fructose was derived from fresh fruit. Both diets were modestly energy-restricted in order to induce weight loss. All participants were instructed to exclude added sugars from processed fruit juices and fruit drinks, sugar-sweetened soft drinks and beverages, and sweetened bakery products such as pies, cakes, strudels, doughnuts, and cookies, in addition to dairy dessert, chocolate, candy, and dried fruits.
  After six weeks, the moderate natural fructose group lost an average of 4.19 kg, while the low-fructose group lost 2.83 kg; the between-group difference in weight loss was statistically significant. The moderate natural fructose group also showed a trend toward greater reduction in blood glucose level.
  What makes the findings from this trial particularly noteworthy is that one of the coauthors, Dr Richard Johnson, published a book called The Sugar Fix in 2009, that discusses the potential role of fructose in the obesity epidemic. Kudos to him for publishing a research finding against his own career and financial interest!
• A systematic review published in 2015 analysed 11 studies of interventions lasting at least three weeks, in which individuals were randomised to either diets high or low in whole, fresh fruit. The highest-quality studies found that those assigned to eat more fruit lost weight, with the greatest weight loss occurring in those who increased their fruit consumption the most.

Fructose myths and misunderstandings

The vilification of fruit by low-carb proponents is largely based on several misunderstandings about the fructose that most fruits contain. Fructose is a simple sugar – called a monosaccharide. When fructose is bound to glucose, it forms sucrose, or table sugar – a disaccharide. Different varieties of fruit contain various mixtures of sucrose, glucose, fructose and certain other sugars such as sorbitol.

Whereas glucose stimulates your pancreas to release insulin, allowing your cells to take up glucose and burn it for energy, fructose does not stimulate insulin secretion and instead is taken up almost entirely by the liver. Under certain circumstances, fructose can be turned into fat, which can either accumulate in the liver causing fatty liver and hepatic insulin resistance; or be sent out into the blood stream, causing systemic insulin resistance, high triglycerides and fat accumulation in adipose tissue.

Sounds scary, right? But what are those ‘certain circumstances’ in which fructose creates such calamities? Quite simply, experimental feeding trials in which obese individuals are fed fructose at levels that no normal human being would or could consume – typically 50 per cent above the 95th percentile of consumption or in other words, half as much again as is consumed by those who eat the most fructose – mostly from ultraprocessed foods – in their regular daily diet! In hypercaloric (deliberate overfeeding) trials, the quantity of fructose fed to volunteers is even more extreme, with a median dose more than twofold higher than the 95th percentile for intake.

In trials which simply substituted an equal-calorie amount of fructose for other carbohydrates normally consumed in the average human diet, there were no adverse effects on body weight, blood pressure, blood fats or insulin level; and in fact a possible benefit was found for glucose tolerance and glycaemic control in diabetics.

The other point to bear in mind here is that fructose in the human diet almost always occurs in combination with glucose, whether in fruit, honey, table sugar or high fructose corn syrup, so trials where fructose is consumed in isolation give very misleading results.

Just how much fructose does fruit contain, anyway? Different fruits have different quantities, but here are the amounts of fructose in commonly-consumed fruits:

• Apple (1 medium): 8-12.5 g, depending on variety
• Banana (1 cup, sliced): 7.3 g
• Blueberries (1 cup): 7.4 g
• Mango (1 cup, sliced): 7.7 g
• Pineapple (1 cup, chunks): 3.5 g
• Raspberries (1 cup): 2.9 g
• Watermelon (1 cup, balls): 5.2 g

And how much fructose was found to wreak metabolic havoc and cause weight gain in experimental feeding trials? 104 to 250 g per day, or between 18 and 97 per cent of total daily energy intake.

So if you’re intending to eat 10 apples or 40 cups of pineapple or 50 cups of raspberries today, you probably need to back off on your fruit consumption. Otherwise, relax and enjoy some of Mother Nature’s dessert, guilt-free!

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1. Dr Robert Atkins died in 2003, at the age of 72. Medical records leaked from the New York City medical examiner’s office indicated that he weighed 117 kg (258 lb) at the time of his death, and had a history of myocardial infarction (heart attack), congestive heart failure and hypertension. Boy, that sounds like a diet I would like to follow. ↩︎