Fructose May Help Control Post-Exercise Cravings - Almost 30% Reduced Desire to Eat After 1h Low-Intensity "Cardio"

Fructose May Help Control Post-Exercise Cravings - Almost 30% Reduced Desire to Eat After 1h Low-Intensity "Cardio"

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About to go for a walk? Have fructose for breakfast to keep the hunger at bay.

I know very well that fructose is the nutritional boogyman of the 21st century, but avoiding it altogether is about as unwarranted as consuming it by the pound is unhealthy. A recent study from the Department of Health and Physical Education at the Hong Kong Institute of Education and the Department of Sports Science and Physical Education at the Chinese University of Hong Kong does now show a new, hitherto unknown, or at least under-appreciated effect of fructose: The ingestion of a fructose containing, albeit not fructose only (not tested, though) breakfast will significantly reduce the desire to eat that will usually rise sharply after a 60 minute bout of "cardio" training in form of walking at 50% of one's individual VO2max.

Learn more about fructose at the SuppVersity

Bad Fructose not so Bad, After All! Learn its Benefits.

Fructose From Fruit is NOT the Problem

Americans Don't Eat More Fructose Today

An Apple A Day, Keeps... & More (Guestpost)

Fructose is Not Worse Than Sugar

How Much Fructose is Bad for the Heart?

As a SuppVersity reader you will know that low-intensity cardio, much more than HIT or HIIT (learn more), will trigger significant increases in hunger and one's desire to eat. To ameliorate this effect, you could - that's at least what the aforementioned study shows - simply replace part of the starchy or high GI carbs of your breakfast with high fructose fruits and/or other fructose containing food items.... that's at least - as  previously mentioned - what the study at hand suggests; a study in which Hong Kong researchers compared the effects of three isocaloric breakfasts with identical amounts of carbs (1.0 g/kg body weight) from different food sources with different GIs (41, 39, and 72) and fructose contents on the appetite scores of ten healthy young male volunteers (21.7 ± 1.5 yr, 20.9 ± 1.1 kg/m²) who had to rate different aspects of appetite every 30 min during the 2-hr postprandial period after the meal, as well as during the 1-hr recovery period that followed the 1h of brisk walking (46% VO2max) all subjects had do perform 2h after consuming the standardized breakfasts.

"Three isocaloric meals were used in the present study. [...] Briefly, all meals had similar macronutrients and provided 1.0 g∙kg−1 body weight CHO for each participant. The LGI meal was composed of cooked spaghetti, egg, and full-fat milk. The LGIF meal comprised rice vermicelli, egg, ham, and fructose. The HGI meal involved rice vermicelli, egg, ham, and glucose. In the LGIF and HGI meals, approximately 25% of energy was derived from the fructose or glucose beverage (nearly 25 g for a 60 kg person). The calculated GI values for the LGI, LGIF, and HGI breakfasts were 41, 39, and 72, respectively. All meals were freshly prepared in the morning of each main trial, and the preparation procedure was standardized."

As you can see in Figure 1 the three test-meals initially had very similar effects on the subjects' appetite ratings, i.e. their desire to eat, hunger, fullness, and perceived ability to eat.

Figure 1: Appetite Sub-Score. b: P < 0.05 vs. LGIF. LGI: Low-GI meal without fructose; LGIF: Low-GI meal including fructose beverage; HGI: High-GI meal (Sun. 2015).

Only the 25% fructose meal, however, kept the rapid increase (or decrease in the case of fullness) in all four parameters after the 1h of brisk walking (Rec-X in Figure 1) at bay. That's quite an interesting observation, even though one could argue that the study cannot serve as a definite litmus test, because it lacks a post-exercise test-meal where the practical significance of the reduced appetite scores was measured against the reduction in food intake in the fructose group.

But isn't fructose the appetite increasing, liver clogging devil? While it may be the devil in the books of a couple of researchers who have nothing else to publish, the specific effect of fructose on appetite are far from being proven to be good or bad. (Rodin. 1990 & 1991). While it appears as if the isolated consumption of high amounts of free fructose has negative effects on appetite control (Lowette. 2015); and still, there's  no debating that fructose has the general ability to blunt food intake compared to an isocaloric amount of glucose in healthy individuals, as it has been shown by Rodin in 1991 (see Figure on the left).

Irrespective of the previously mentioned methodological short-coming, it is, as the authors highlight, quite striking that "the increased fructose content in LGIF breakfast suppressed the appetite score, compared with isocaloric HGI and LGI breakfast" (Sun. 2015). Previously, scientists often argued that the satiety promoting effect of fructose must be mediated by the lower GI and correspondingly lower insulin spikes as well as reduced glucose excursions after fructose vs. glucose containing meals. The data in Figure 2, however, tells us that neither the insulin spikes (Figure 2, right) nor the glucose excursions (Figure 2, left) differed significantly between the LGI (low GI) and the LGIF (low GI + fructose) meals over the relevant last part of the study period - an observation which does by the way also show us that "[w]hen exercise is included as a co-intervention strategy, the effect of GI on appetite may be highly complex" (Sun. 2015) and in most cases relatively irrelevant.

Figure 2: Glucose and insulin response to the test meals; significant differences were observed for high GI (HGI) compared to the other meals and initially for the fructose meal, where the glucose levels increased slightly more rapidly than in the low GI (LGI) reference meal -  in spite of identical calculated GI values, by the way (Sun. 2015)

Previous studies show that even though exercise exerts the most profound effect on human energy expenditure, it seems that post-exercise energy intake is not affected by exercise itself (Blundell. 1999; Melzer. 2005). In that, a study by Stevenson et al appears to confirm the finding of the study at hand which is that there is no difference relevant appetite scores between HGI and LGI trials during the postprandial period if the time between breakfast and moderate intensity exercise is sufficiently long.

Figure 3: The appetite suppressing effects of fructose preloads in the absence of exercise have been known ever since Rodin's 1990 study on the effects of fructose vs. glucose and water preloads on food intakes (Rodin. 1990).

What's new with the present study, though, is that "eating an LGIF [25% fructose] breakfast resulted in decreased appetite scores compared with HGI breakfast and LGI breakfast [25% non-fructose carbs]" (Sun. 2015). This and the fact that this difference cannot be explained by the usual suspects, i.e. insulin and blood glucose levels leads Sun et al to emphasize that ...

"[t]he effect of fructose on appetite has been substantially investigated. Earlier studies have indicated that fructose beverages suppressed energy intake more than glucose beverages did (Rodin, 1990 and Rodin, 1991). The underlying mechanism has been attributed to the metabolism of fructose in the liver and the effect of insulin" (Sun. 2015).

In fact, scientists have previously speculated that fructose may affect appetite through slow and incomplete absorption. This effect, however, is eliminated when fructose is consumed with other CHOs (Anderson. 2003). As far as potential mechanisms are concerned, we are thus left with changes in satiety hormones and peptides like ghrelin, cholecystokinin, glucagon-like-peptide-1 and peptide-YY and/or direct or indirect effects on the gut-brain axis as potential mechanisms that would explain the results of Sun's study. Unfortunately, neither of these mechanism was assessed in their study.

Make you choice - cholesterol and regular sugar (left), or fat free and fructose-laden? In the end it all may not even matter. In spite of that, you shouldn't forget that fruit is not the enemy, isolated fructose in drinks is.

So, what's the verdict? I'd like to cite the original conclusion first, before adding my two cents: "It appears that fructose content in, rather than the GI of, a pre-exercise breakfast meals affect subjective appetite score during the recovery period after 1-hr of brisk walking" (Sun. 2015).

There's no doubt that this is right, but there are important qualifications with respect to the real-world significance of the results: Firstly, the absence of a post-recovery test meal, where the actual food intake would have been measured, is a major methodological problem of the study at hand. Even though changes in appetite of a similar magnitude will usually translate in changes in food intake, this is not a necessity. Therefore the actual food intake and the mechanism for the appetite suppression have to be elucidated in future trials.

In the mean time, I'd suggest you do your own test-run. If it works, fine. If not, you don't have to care about the results of follow-up studies, anyway. Why? Well, what works for the virtual average study participant does not necessarily have to work for you | Comment on Facebook!

References:

• Anderson, G. Harvey, and Dianne Woodend. "Effect of glycemic carbohydrates on short-term satiety and food intake." Nutrition Reviews 61.5 (2003): S17.
• Blundell, John E., and Neil A. King. "Physical activity and regulation of food intake: current evidence." Medicine and science in sports and exercise 31 (1999): S573-S583.
• Lowette, Katrien, et al. "Effects of high-fructose diets on central appetite signaling and cognitive function." Frontiers in nutrition 2 (2015).
• Melzer, Katarina, et al. "Effects of physical activity on food intake." Clinical nutrition 24.6 (2005): 885-895.
• Rodin, Judith. "Comparative effects of fructose, aspartame, glucose, and water preloads on calorie and macronutrient intake." The American journal of clinical nutrition 51.3 (1990): 428-435.
• Rodin, Judith. "Effects of pure sugar vs. mixed starch fructose loads on food intake." Appetite 17.3 (1991): 213-219.
• Sun, Feng-Hua, Stephen Heung-Sang Wong, and Zhi-Gang Liu. "Post-exercise appetite was affected by fructose content but not glycemic index of pre-exercise meals." Appetite 96 (2016): 481-486.

Breakfast: Eat it or Skip it? Making it High Protein Will Have Habitually Skipping Teens Lose Fat & Curbs Their Hunger

Breakfast: Eat it or Skip it? Making it High Protein Will Have Habitually Skipping Teens Lose Fat & Curbs Their Hunger

adolescents Body Fat breakfast dieting high protein lose body fat lose fat normal protein teens

This could have been the HP breakfast. Egg-based pancakes + ham.

It is almost like the question "to carb" or "not to carb" and the almost religiously maddish discussions between carb-eaters and ketophiles: The debate revolving around the useful- or uselessness of breakfast, when it comes to health and physique issues.

In my more recent articles about the topic I have repeatedly exposed the claim that "not having breakfast is bad for everyone" is total bogus; and while I am not going to go back on that I am about to discuss a study that demonstrates that the right breakfast, i.e. one that's high in protein, may be extremely better than having no breakfast at all.

Learn more about fasting and eating / skipping breakfast at the SuppVersity

Breakfast and Circadian Rhythm

Does Meal Timing Matter?

Breakfast & Glucose Metab.

Break the Fast, Cardio & the Brain

Does the Break- Fast-Myth Break?

Breakfast? (Un?) Biased Review

Said study has been conducted by scientists from the University of Missouri and the Purdue University (Leidy. 2015). It's an investigation into the effects of normal-protein (NP) vs. high-protein (HP) breakfast meals on appetite control, food intake, and body composition in “breakfast skipping” young people with overweight/obesity.

As a SuppVersity reader you'll know that previous studies suggest that as habitual breakfast skippers, the youths are actually not the ideal study object for a study to show beneficial effects of breakfast. After all, a recent study by Thomas et al. showed quite convincingly that "Whether Skipping Breakfast Increases Insulin, Hunger and Blood Lipids Depends on One's Breakfast Habits" (read the article). Is this a problem? Well, it could be if the new study yielded negative results. After all, we'd have to argue that this was to be expected if the subjects were habitual breakfast skippers.

Table 1: Subject characteristics at baseline (Leidy. 2015). As you can see the subjects were randomly assigned to the three groups at a ratio of 1:2:2 to breakfast skipping, normal protein (NP) and high protein (HP) breakfast.

Luckily, the results were positive and the study with its 12-week study period probably long enough to overcome the effects of habituation which mess with the results of all studies which test the effect of having vs. skipping breakfast on only one or two occasions.

Figure 1: Macronutrient composition (g) of the test meals used in the study (Leidy. 2015)

The study at hand, however, had its fifty-seven adolescent subjects (age: 19 +/- years; BMI: 29.7 +/- 4.6 kg/m²) complete a 12-week randomized controlled trial in which the adolescents consumed either a 1,464 kJ NP breakfast (13 g protein), an isocaloric breakfast with a high protein content (HP | 35 g protein), or continued to skip breakfast (CON). The main outcome variables were the subjects' pre- and post-study appetite, their food intake, body weight, and body composition, which was assessed assessed via DXA scans (which are as you know still the "gold standard" for measuring the body composition of subjects in scientific studies)

In Schlundt's 12-week study in which the subjects had to follow the same energy reduced diet pattern one time with, one time without breakfast the marginal differences in weight loss and fat loss (the former favors breakfast, the latter skipping it) were just as statistically non-significant as the other inter-group differences the US scientists observed (Schlundt. 1992).

In the long run, calories count. So if you are counting calories it doesn't matter if you have breakfast or don't. There are bazillions of "breakfast eating vs. skipping"-studies, but this is only study #3 to test the long-term effects. Yes, sometimes science is pathetic and stupid - and trying to elucidate the health effects of eating vs. skipping breakfast in studies on three testing days is both: pathetic and stupid.

One of the two non-pathetic studies comes from Schlundt et al. who examined the effects of consuming breakfast vs. breakfast skipping during a 12-week energy restriction weight loss diet in 52 adult women with obesity without finding significant differences.

More recently, Dhurandhar et al. completed a 16-week study in 309 adults with obesity and included a general recommendation to either "eat breakfast" or "skip breakfast". As it was to be expected when energy intake is controlled for, again, no differences in weight loss were observed in those who began eating breakfast compared to those who continued to skip breakfast.

The NP and HP groups were provided with specific breakfast meals to consume between 6:00 and 9:45am each day, while the CON group continued to skip breakfast (with nothing to eat/drink, besides water) before 10:00am - with significant consequences as the in parts significant inter-group differences in Figure 2 can tell you.

Figure 2: Comparison of the changes in fat mass, the daily food intake, hunger and fullness ratings in the subjects from the CON (=kept skipping breakfast), NP (normal protein) and HP (high protein) breakfast groups (Leidy. 2015).

The superiority of (a) having breakfast and (b) consuming a high protein breakfast are not debatable. With its 12-week study duration, the study at hand obviously allowed for a full habituation and did thus - much in contrast to many short-term studies - yield all the benefits that are usually ascribed to having breakfast. In particular, having breakfast...

• 

  "Breakfast!? An (Un-)Biased (?) Review of the Breakfast Myth" | read it!

  made the subjects magically lose (HP) or at least not gain (NP) superfluous body fat.
• significantly reduced the daily energy intake in the high protein condition and buffered the significant increase in energy intake in the no breakfast condition if the breakfast had a normal protein content,
• reduced the total time during which the subjects were hungry not just in the morning, but 24/7, and
• increased the subjects' fullness, especially in the morning.

In that it's important to highlight that the high protein breakfast outperformed the normal protein breakfast in all relevant categories, i.e. change in body fat, change in daily energy intake and change in hunger ratings, Accordingly, Leidy et al. are right when they highlight only the high protein breakfast in their conclusion which says that

"daily addition of a HP breakfast improved indices of weight management as illustrated by the prevention of body fat gain, voluntary reductions in daily intake, and reductions in daily hunger in breakfast skipping adolescents with overweight/obesity." (Leidy. 2015)

In spite of that, we should not forget that even a regular breakfast which contained 15% protein, 65% carbohydrates, and 20% fat and consisted of (you guessed it) ready-to-eat cereals with milk outperformed not having breakfast at all. That's in contrast to some previous studies, most of which used shorter study durations and didn't allow for the habituation that's necessary for breakfast to have effects on the total energy intake, for example, to take place.

The study at hand is an excellent example that shows that the previously observed effects of habitation can be overcome if you adhere to your new breakfast protocol meticulously. 

So what? If you have a teenage son or daughter, serve him / her a high protein breakfast containing 40% protein, 40% carbohydrates, and 20% fat, like an egg-based pancakes and ham; egg-based waffles with pork-sausage; egg and pork scramble; and an egg and pork burrito (all these were options the subjects in the study at hand were provided with on a weekly basis. It's going to help them manage their weight, food cravings, and hunger pangs and it's not going to take you an hour to prepare (rather 15 min - max). The scientists assertion that "it is unclear as to whether the daily consumption of a high-protein breakfast, containing 35 g of protein, is feasible in a free-living environment" (Leidy. 2015) is just more pathetic evidence that people care so little about their health that they'd rather die from eating ready-made cereals than to invest the 10-15 minutes to prepare delicious and healthy protein pancakes into their health.

If you are now contemplating to switch back to having breakfast, yourself, let me remind you that it is not possible to extrapolate study results that were generated with a specific group of subjects, in this case overweight, but still healthy adolescents to whomever you want. If you are on an energy controlled diet and skipping breakfast as a means to do intermittent fasting and reduce your overall energy intake, you won't reduce your 24h energy intake (after all, you're eating X kcal everyday, anyway).  It is thus unlikely that you'd lose more weight than you'd do without breakfast and if you are like many people you will probably even feel hungrier now that you're able to eat only 3 small vs. 1-2 large(r) meals | Comment on Facebook!

References:

• Dhurandhar, Emily J., et al. "The effectiveness of breakfast recommendations on weight loss: a randomized controlled trial." The American journal of clinical nutrition 100.2 (2014): 507-513.
• Leidy, Heather J., et al. "A high‐protein breakfast prevents body fat gain, through reductions in daily intake and hunger, in “Breakfast skipping” adolescents." Obesity (2015).
• Schlundt, David G., et al. "The role of breakfast in the treatment of obesity: a randomized clinical trial." The American journal of clinical nutrition 55.3 (1992): 645-651.
• Thomas, Elizabeth A., et al. "Usual breakfast eating habits affect response to breakfast skipping in overweight women." Obesity 23.4 (2015): 750-759.