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Fructose, Sugar, Obesity and You!

QUESTION; There are many stories about the evils of fructose and high fructose corn syrup, many of them coming from a Dr Lustig. So, is high fructose corn syrup metabolized differently by the liver than glucose? If so, does this make it worse for us or better?

Yes. Fructose is metabolized a little differently, but in regard to your health, as long as you keep the level of intake of "all" added sugars to a minimum (< 5% of calories), it is completely irrelevant. So, it’s "much ado about nothing."

Dr Lustig means well, but his focus is really off-base and misguided as well as misleading as I will explain.

Sugar, if used, should be nothing more than an occasional condiment. I recommend < 5% of calories to come from any added refined/concentrated sugar, regardless if it is natural, whole, processed, etc. At this level, even in all the studies on fructose, as you will see below, you can't find any evidence of harm.

Let's step back for a minute and put all of this in proper perspective...

It is important to remember that in toxicology, there are a few guiding principles, including the classic, "the dose makes the poison." And, besides dose, route, time, duration, rate and frequency of exposure, all matter as do things like age, gender, environment, and the vitality of the host.

Most chemicals display a dose response curve and only a few chemicals have no well-defined safe level of exposure and there are also a few that bio-accumulate over time. All of this matters in any discussion of toxicity.

In regards to sugars (caloric, artificial, natural, etc), this all matters as none of them, are likely toxic at any level in low occasional doses.

In addition, in regard to diet and health, dietary patterns clearly trump individual foods, good or bad. Unfortunately, our current dietary pattern is so unhealthy and already contains higher than low occasional doses for most things that may be harmful.

The AHA recently came out with some "prudent upper limits" for added sugars, which comes out to about 4-7% of calories and the WHO has said less than 10%. I agree with the AHA and think the ~5% is probably safer especially considering the current overall pattern and that added sugars make up about 16-20% of calories.

I like to think of this in regard to 4 options:

1) Someone who has a very healthy diet and lifestyle and adds a small amount of any of the sugars:

I do not see this as being harmful or mattering.

2) Someone who has a very healthy diet and lifestyle and adds a large amount of any of the sugars:

This could have a negative impact on their otherwise healthy diet and lifestyle due to the amount.

3) Someone who has a very unhealthy diet and lifestyle and adds a small amount of any of the sugars:

I do not see this as being harmful nor would I see it as the main issue for this person. Due to their unhealthy diet and lifestyle, they have much bigger issues to tackle than a small amount of sugar.

4) Someone who has a very unhealthy lifestyle and adds a large amount of any of the sugars:

Again, the large amount of added sugars may have an added negative impact but they already have much bigger issues to worry about.

So, to me, again, the key issue always comes back to the dose and perspective.

Therefore, my professional and personal opinion is that I would care little about the occasional low dose use of any sugar as part of an overall healthy lifestyle and dietary pattern, especially if the occasional use makes the adherence to the healthy dietary lifestyle easier.

The only exception would be someone who had a specific sensitivity/allergy to any one of them in which case, I would recommend they avoid any such one.

QUESTION: I have also heard that because of the way it is metabolized, fructose is a major contributor to the obesity epidemic.

Again, let’s step back and take a close look at these claims.

Attributing the obesity epidemic to HFCS is misguided and there is no real credible evidence supporting it. And, while all sugary drinks and any liquid calories (regardless of the type of sugar) have been a contributor to the obesity epidemic, sugary drinks (with or without fructose) are not in-and-of-itself the "main" cause of obesity as some claim.

The primary cause of the obesity epidemic is energy imbalance, and many things have contributed to this including behavioral and environmental

Most of the "dramatic" increase in HFCS is because it served as a replacement for the concurrent decrease in sucrose. It replaced sucrose. The increase in total energy since 1970 from all sugars (14%) does not correlate to the increase in obesity. In addition, the intake from total sugars is down 8% since its peak in 1999, yet obesity rates still rise.

More importantly, the consumption of HFCS is actually down around 9% in the last 10 years from when it also peaked in 1999 but obesity rates continued to rise dramatically during this same time.

So, consumption of HFCS has actually decreased more than total sugars, so if HFCS was more of a primary cause then just sugar, we would have seen a decrease in obesity rates and it has now been about 10 years since this decline in sugar and HFCS started. So, while some say that the increase in obesity is said to correlate with the increase in HFCS, we see that this is just not true. (This data is freely available at the USDA ERS website)

Let’s look at some of the evidence.

American Journal of Clinical Nutrition, Vol. 86, No. 6, 1577-1578, December 2007 Much ado about high-fructose corn syrup in beverages: the meat of the matter

Unfortunately the recent focus on HFCS has done little to resolve the role of sugars in contributing to energy imbalance. The hypothesis that the replacement of sucrose with HFCS in beverages plays a causative role in obesity is not supported on the basis of its composition, biologic actions, or short-term effects on food intake. Had the hypothesis been phrased in the converse, namely that replacing HFCS with sucrose in beverages would be a solution for the obesity epidemic, its merit would have been seen more clearly. Put simply, a proposal that a return to sucrose-containing beverages would be a credible solution to the obesity epidemic would have been met with outright dismissal. In many countries where trade barriers have prevented the replacement of sucrose with HFCS, the prevalence of obesity is high. Therefore, what role HFCS in beverages plays in the etiology of obesity, as in Much Ado about Nothing (1), may simply be a play on words.


S.Z. Sun, M.W. Empie / Food and Chemical Toxicology 45 (2007) 1523–1536 Lack of findings for the association between obesity risk and usual sugar-sweetened beverage consumption in adults – A primary analysis of databases of CSFII-1989–1991, CSFII-1994–1998, NHANES III, and combined NHANES 1999–2002

Populations who frequently consumed SSB (Sugar Sweetened Beverages), primarily HFCS sweetened beverages, did not have a higher obesity rate or increased obesity risk than that of populations which consumed SSB infrequently.


Am J Clin Nutr. 2007 Dec;86(6):1586-94.No differences in satiety or energy intake after high-fructose corn syrup, sucrose, or milk preloads

CONCLUSION: Energy balance consequences of HFCS-sweetened soft drinks are not different from those of other isoenergetic drinks, eg, a sucrose-drink or milk.


Crit Rev Food Sci Nutr. 2007;47(6):561-82. A critical examination of the evidence relating high fructose corn syrup and weight gain.

Based on the currently available evidence, the expert panel concluded that HFCS does not appear to contribute to overweight and obesity any differently than do other energy sources.


Am J Clin Nutr. 2008 May;87(5):1194-203.Twenty-four-hour endocrine and metabolic profiles following consumption of high-fructose corn syrup-, sucrose-, fructose-, and glucose-sweetened beverages with meals.

CONCLUSIONS: Sucrose and HFCS do not have substantially different short-term endocrine/metabolic effects. In male subjects, short-term consumption of sucrose and HFCS resulted in postprandial TG responses comparable to those induced by fructose.

From the latest review...

Effect of Fructose on Body Weight in Controlled Feeding Trials

A Systematic Review and Meta-analysis (The Cochrane Review)

Ann Intern Med. 2012;156:291-304.

Limitations: Most trials had methodological limitations and were of poor quality. The weight-increasing effect of fructose in hyper- caloric trials may have been attributable to excess energy rather than fructose itself.

Conclusion: Fructose does not seem to cause weight gain when it is substituted for other carbohydrates in diets providing similar calories. Free fructose at high doses that provided excess calories modestly increased body weight, an effect that may be due to the extra calories rather than the fructose.

Now, as we see from the studies I will list below, fructose can create problems as it goes directly to the liver However, these problems only exist when excess is consumed.

From the studies below, depending upon which variable they are looking at, it takes a minimum of 50 grams of fructose to see any negative effect and at least 100 grams of fructose to see any real negative effect.

For 50 grams fructose this would be the equivalent of either 100 grams of sucrose as sucrose is 50/50 glucose/fructose and about 91 grams of HFCS as HFCS is 55/45 fructose/glucose.

91 grams of HFCS is 370 calories

100 grams of sucrose is 420 calories

For 100 grams this would be the equivalent of either 200 grams of sucrose as sucrose is 50/50 glucose/fructose and about 182 grams of HFCS as HFCS is 55/45 fructose/glucose.

182 grams of HFCS is 740 calories

200 grams of Sucrose is 800 calories

I think anyone would agree that getting 370 to 420 calories, let alone 740 to 800 calories of either one as part of one’s daily diet would be considered excess. On a 2000 calorie diet, this would be 18.5% (at 370 calories) to 40% (at 800 calories) of someone's caloric intake. At 3000 calories, this would be 12% to 27% of someone’s caloric intake.

So, the real issue is not which one, but the total amount.

In this study, we see some impact from fructose, but the fructose was making up 25% of their calories, which is extremely high.

Br J Nutr. 2008 Nov;100(5):947-52. Consumption of fructose-sweetened beverages for 10 weeks increases postprandial triacylglycerol and apolipoprotein-B concentrations in overweight and obese women.

Fructose consumption in the USA has increased over the past three decades. During this time, obesity, insulin resistance and the metabolic syndrome have also increased in prevalence. While diets high in fructose have been shown to promote insulin resistance and increase TAG concentrations in animals, there are insufficient data available regarding the long-term metabolic effects of fructose consumption in humans. The objective of the present study was to investigate the metabolic effects of 10-week consumption of fructose-sweetened beverages in human subjects under energy-balanced conditions in a controlled research setting. Following a 4-week weight-maintaining complex carbohydrate diet, seven overweight or obese (BMI 26.8-33.3 kg/m2) postmenopausal women were fed an isoenergetic intervention diet, which included a fructose-sweetened beverage with each meal, for 10 weeks. The intervention diet provided 15% of energy from protein, 30% from fat and 55 % from carbohydrate (30% complex carbohydrate, 25% fructose). Fasting and postprandial glucose, insulin, TAG and apoB concentrations were measured. Fructose consumption increased fasting glucose concentrations and decreased meal-associated glucose and insulin responses (P = 0.0002, P = 0.007 and P = 0.013, respectively). Moreover, after 10 weeks of fructose consumption, 14 h postprandial TAG profiles were significantly increased, with the area under the curve at 10 weeks being 141 % higher than at baseline (P = 0.04). Fructose also increased fasting apoB concentrations by 19 % (P = 0.043 v. baseline). In summary, consumption of fructose-sweetened beverages increased postprandial TAG and fasting apoB concentrations, and the present results suggest that long-term consumption of diets high in fructose could lead to an increased risk of CVD. PMID: 18384705

This article is where the 50-100 gram limits comes from...

Am J Clin Nutr. 2008 Nov;88(5):1419-37. Fructose consumption and consequences for glycation, plasma triacylglycerol, and body weight: meta-analyses and meta-regression models of intervention studies.

BACKGROUND: The glycemic response to dietary fructose is low, which may improve concentrations of glycated hemoglobin (HbA(1c), a marker of dysglycemia). Meanwhile, adverse effects on plasma triacylglycerol (a marker of dyslipidemia) and body weight have been questioned. Such effects are reported inconsistently. OBJECTIVE: We aimed to evaluate the effect of fructose on these health markers, particularly examining treatment dose and duration, and level of glycemic control. DESIGN: A literature search was conducted for relevant randomized and controlled intervention studies of crystalline or pure fructose (excluding high-fructose corn syrup), data extraction, meta-analyses, and modeling using meta-regression. RESULTS: Fructose intake < 90 g/d significantly improved HbA(1c) concentrations dependent on the dose, the duration of study, and the continuous severity of dysglycemia throughout the range of dysglycemia. There was no significant change in body weight at intakes <100 g fructose/d. Fructose intakes of <50 g/d had no postprandially significant effect on triacylglycerol and those of <or=100g/d had no significant effect when subjects were fasting. At >or=100 g fructose/d, the effect on fasting triacylglycerol depended on whether sucrose or starch was being exchanged with fructose, and the effect was dose-dependent but was less with increasing duration of treatment. Different health types and sources of bias were examined; they showed no significant departure from a general trend. CONCLUSIONS: The meta-analysis shows that fructose intakes from 0 to >or=90 g/d have a beneficial effect on HbA(1c). Significant effects on postprandial triacylglycerols are not evident unless >50 g fructose/d is consumed, and no significant effects are seen for fasting triacylglycerol or body weight with intakes of <or=100 g fructose/d in adults. PMID: 18996880

This latest article shows some impact, though minimal, from just 40 grams of fructose. However, 40 grams of pure fructose (which is not how we consume it) is 160 calories. If we limit total sugars to no more than 5% of calories, that would be 25 grams at 2000 calories and 37 grams at 3000 calories. So, my guidelines still work because fructose is always part of another sugar at anywhere from 50-70% so we would still be way below any potential level of impact.

Am J Clin Nutr August 2011 ajcn.013540. Low to moderate sugar-sweetened beverage consumption impairs glucose and lipid metabolism and promotes inflammation in healthy young men: a randomized controlled trial

Background: Sugar-sweetened beverages (SSBs) have unfavorable effects on glucose and lipid metabolism if consumed in high quantities by obese subjects, but the effect of lower doses in normal-weight subjects is less clear.

Objective: The aim was to investigate the effects of SSBs consumed in small to moderate quantities for 3 wk on LDL particle distribution and on other parameters of glucose and lipid metabolism as well as on inflammatory markers in healthy young men.

Design: Twenty-nine subjects were studied in a prospective, randomized, controlled crossover trial. Six 3-wk interventions were assigned in random order as follows: 600 mL SSBs containing 1)40 g fructose/d [medium fructose (MF)], 2) 80 g fructose/d [high fructose (HF)], 3) 40 g glucose/d [medium glucose (MG)], 4) 80 g glucose/d [high glucose (HG)], 5) 80 g sucrose/d [high sucrose (HS)], or 6) dietary advice to consume low amounts of fructose. Outcome parameters were measured at baseline and after each intervention.

Results: LDL particle size was reduced after HF by −0.51 nm (95% CI: −0.19, −0.82 nm) and after HS by −0.43 nm (95% CI: −0.12, −0.74; P < 0.05 for both). Similarly, a more atherogenic LDL subclass distribution was seen when fructose-containing SSBs were consumed (MF, HF, and HS: P < 0.05). Fasting glucose and high-sensitivity C-reactive protein (hs-CRP) increased significantly after all interventions (by 4–9% and 60–109%, respectively; P < 0.05); leptin increased during interventions with SSBs containing glucose only (MG and HG: P < 0.05).

Conclusion: The present data show potentially harmful effects of low to moderate consumption of SSBs on markers of cardiovascular risk such as LDL particles, fasting glucose, and hs-CRP within just 3 wk in healthy young men, which is of particular significance for young consumers.

Now, as you may see in the above study (AJCN 2008), fructose does lower BS and A1c but that may not always be a good thing. The reason fructose, and sweeteners high in fructose do not affect the BS or GI as much, is because they fructose is metabolized a little different and bypasses the bloodstream and goes directly to the liver. Being it bypasses the bloodstream you see little effect on BS and/or GL. However, in excess, in the liver, it can cause elevated levels of triglycerides and increase someone’s risk for heart disease. In excess, it may also increase the risk of metabolic syndrome/insulin resistance and these effects are most likely in those who are insulin resistant, and/or overweight and/or obese.

So, it is a double-edged sword but again, in the end, quantity is the real issue. If you do all the math, as I have tried to show above, you will see that no matter which one you choose, keeping it under 5% of your total calories is the real issue. At 10%, you can being to approach the levels that may begin to show some harm from those that are higher in fructose.

Two last points:

- Some HFCS has been shown to be contaminated with Mercury, so that is a separate but potentially important issue.

- Agave syrup, is which is now so popular amongst the health conscious, is 70-90% fructose and being billed as low in the GI. Well, maybe so, but it also will effect TGs more than HFCS so it is clearly not a health food or a better choice.

The bottom line, no matter which one you choose to use, quantity is the real issue.

QUESTION: What about fruit? Isn’t fruit mostly fructose?

Fruit is OK is because it has way more fiber than fructose. The fiber in fruit slows down the absorption of glucose, fructose, and fatty acids from the gut, while increasing the rate of transit which helps to trigger the satiety signal earlier.

This is important because the rate of fructose absorption determines how fast the fructose will hit the liver. The faster it reaches the liver (since the liver has a fixed capacity for extraction and metabolism), the more likely the liver will be overwhelmed by the excess and that more will end up as liver fat, causing insulin resistance.

The fiber in fruit limits the volume of fructose consumed (through its high satiety) and the rate of absorption, thus sparing the liver.

In other words, enjoy your fruit. :)

QUESTION: Can you help me understand what 5% of calories from added sugar looks like in my day, in packaged food and in a recipe?

Sure, first, make sure the majority of your calories come from unprocessed and/or minimally processed plant foods. If you are consuming about a 2000 calorie diet, 5% of calories would be 100 calories. A Tbsp of sugar is about 50 calories, so that would allow you to add “up to” 2 TB of an added sugar per day if you so desired. I am not recommending that you do this, but showing you how to keep your intake of added sugars to 5% or less.

The problem arises when you include packaged foods that have added sugars in them. The reason is, the Nutrition Facts Label does not list “added” sugars but only “total” sugars which makes it impossible to calculate the amount of just “added” sugars and it is possible that a food has both. So, here is what you can do to help limit added sugars in packaged products.

The simple way: Check the ingredient list. Ingredients are listed by weight. See if the ingredients list added sugars and if it does, the further down the list the better as the amount of added sugar will be less. Best case scenario, avoid any products with any added sugars. Next best case scenario, make sure that if there are any added sugars, that they are not in the first 3-5 ingredients so if they are there, they are in smaller amounts.

A more complicated way: If a product has any added sugars listed in the ingredient list, go to the Nutrition Facts Label and see how many “total” sugars are listed. It will be in grams. Take this number and multiply it by 4. This will give you the calories from total sugar. Now, take this number and divide it by the total calories. This will give you the percent of calories from total sugar. If the percent of calories from total sugars is less than 5%, you can be sure that the amount of any “added” sugars is also less than 5%.

Neither of the above two ways are perfect but the fault lies in the Nutrition Facts Label and with the Food Industry who has fought and won a battle for decades to keep the amount of “added” sugars off the Nutrition Facts Label.

Best of all, minimize the intake of all and any packaged products outside my list of The 10 Healthiest Packages Products!

In regard to a recipe, you can use a recipe (&/or nutrition) analysis program to input the recipe and see how much the sugar is contributing. You can do the analysis either for the whole recipe or per serving. Just remember that every gram of sugar contributes 4 calories. So, if the total recipe is 400 calories, than the added sugars should contribute no more than 20 calories, which would be 5 grams.

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