Tag: research

Does a High Fat Breakfast Burn More Fat?

by Monica Reinagel, MS, LDN

Hold the skim latte and bring on the butter? High-fat breakfasts are enjoying a comeback in some circles, after a study published in the International Journal of Obesity found that rats who ate a high fat breakfast burned more fat throughout the day than rats who ate a high carbohydrate breakfast.

But the reality on the ground looks a little different. Multiple studies have found that people who eat high fat breakfasts end up eating more calories over the course of the day–almost certainly trumping any increase in the fat-burning metabolism observed in the mouse study.

That’s not to say that a breakfast high in refined carbohydrates (corn flakes, toast, jelly, juice, etc.) is the way to go.  The ideal breakfast for appetite and weight control appears to be one that’s high in both protein and fiber. So bring on the eggs, tofu, cottage cheese, yogurt, oatmeal and other whole grain cereals.

As a bonus, research suggests that this type of low-glycemic breakfast may help you burn more fat during your lunch-time workout.

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Special Live Event!

Join me tomorrow night, March 8th, at 9pm Eastern for a forum on breakfast, fitness, and weight management. Joining me for this live webcast are Ben Greenfield of BenGreenfieldFitness.com, Darya Pino, PhD of  SummerTomato.com, and Gloria Tsang, MS, RD of Healthcastle.com.  Your questions and comments are welcome.  The event will be broadcast right here on NutritionOverEasy.com.  Click here to RSVP.

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The Studies:

Time-of-day-dependent dietary fat consumption influences multiple cardiometabolic syndrome parameters in mice.

Energy and macronutrient composition of breakfast affect gastric emptying of lunch and subsequent food intake, satiety and satiation.

The effects of high-carbohydrate vs high-fat breakfasts on feelings of fullness and alertness, and subsequent food intake

Fat oxidation during exercise and satiety during recovery are increased following a low-glycemic index breakfast in sedentary women.

 

Does Caffeine Increase Fat-Burning During Exercise?

by Monica Reinagel, MS, LDN

Q. I read recently that the consumption of caffeine prior to exercise will assist the body in using body fat as fuel, up from 21% to 40%. The remaining fuel comes from stored carbs. Any truth to the story?

A. There may be a grain of truth to the story but not much more.  Taking caffeine  before exercise has been shown to increase energy expenditure (the number of calories burned) during exercise by around 10%.  So if you would normally burn 200 calories in a half-hour, some extra caffeine might help you burn 220.  Continue reading “Does Caffeine Increase Fat-Burning During Exercise?” >

Looking For the Truth on Fructose? Keep Looking.

by Monica Reinagel, MS, LDN

I really don’t get it. Fructose is the dietary scapegoat of the decade, blamed for everything from obesity to liver disease. Never mind that most high fructose corn syrup is in actuality no higher in fructose than regular table sugar. Never mind that the increase in fructose consumption (the so-called smoking gun) over the last ten years was accompanied by an equivalent increase in glucose consumption. Never mind that pure fructose is not found in nature or in the normal human diet–it is virtually always consumed in combination with other sugars.

There is so much myth and hysteria circulating about fructose, you would think some solid scientific inquiry would help clarify the situation. But how are we ever going to figure out what part (if any) fructose per se plays in our health problems when researchers continue to design studies that fail to isolate the variables?

For example, this latest study, published in the American Journal of Clinical Nutrition compared a diet that was high in fructose and and also provided a third too many calories with a diet that contained less fructose and the proper number of calories. Those on the “high fructose” diet experienced several unfavorable changes in their blood lipid profiles.

So what? How many of those effects were due to simply overeating? Why not compare two diets with the same number of calories but differing amounts of fructose? And please don’t show me studies that compare diets containing only fructose versus diets containing only glucose because these type of diets don’t occur outside a laboratory.

Is too much sugar to blame for many of our health woes? You bet. Is fructose metabolized differently than glucose and other sugars? For sure.  Is fructose poison to our bodies? Fructose is like any other sugar molecule: when refined, concentrated, and consumed in excess quantities, it’s not good for you.

Want to improve your health? Cut down on added sugars–that includes table sugar, HFCS, maple syrup, honey, agave nectar, fruit juice concentrates, and foods made with any of these. You’ll be cutting down on fructose in the process–if that makes you feel better.

But I’ve yet to be convinced that fructose is harmful except in cases where sugar (in general) makes up too large a proportion of calories. In these cases, the effects of fructose on the liver and blood lipids are simply one of the mechanisms by which too much sugar damages human health–no more or less dangerous than any number of other mechanisms, such as the effect of glucose on blood sugar and insulin levels, or the effect of excessive calorie intake on body fat and weight.

Let’s Put This New Fructose Study In Perspective

by Monica Reinagel, MS, LDN

A recently published study is going to fuel the hysteria over high-fructose corn syrup. It’s a terrific study. But, contrary to the headlines you are sure to see over the next days and weeks, it does NOT prove that high fructose corn (HFCS) syrup is the cause of the obesity epidemic. Let’s take a closer look.

Researchers at the University of Florida found that rats who were fed a diet that was very high in fructose eventually became resistant to the hormone leptin.  Leptin is a hormone that regulates your appetite and disposition toward weight gain.  In the second half of the study, they switched the leptin-resistant rats to a high-calorie (high-fat) diet. The rats ate a lot more and gained a lot more weight than rats who had not been on a high-fructose diet. (Read more about the study: “Fructose hampers hormone that controls appetite.“)

Now, what does this tell us about the effects of high-fructose corn syrup on humans? Very little.

Aside from the obvious issue (the study was done in rats, not humans), the study had absolutely nothing to do with high fructose corn syrup. The diet that brought about leptin resistance was about 60% fructose, and contained no other form of sugar.  The typical (awful) American diet contains about 35% sugar, about half of which (roughly 17%) is in the form of fructose.

Incidentally, if every bit of HFCS in the food supply was replaced by regular old cane sugar, our fructose intake would still be around 17%.  That’s because high fructose corn syrup contains about the same amount of fructose as sugar.

Like the best research studies, this one poses far more questions than it answers. For example, I’m dying to know whether you’d get the same results at 50% fructose. Or 40% or 30%. What’s the threshold at which the effect starts to set in?

Secondly, I’d love to know whether you’d get leptin resistance with similar amounts of glucose or sucrose?  In other words, how much of this effect is specific to fructose and how much is just sugar? What’s more significant: the amount of total sugar in the diet or the amount of fructose? How does dietary fat affect things? (In the study, the rats ate an extremely low-fat (5%) diet and the fat was lard.)

I imagine that researchers are queuing up to design studies that will answer these questions and more. (And we’re still only talking about rats…)

Those who read this blog (or listen to my podcast) know that I think the hysteria over high-fructose corn syrup is misplaced. We should be alarmed by the amount of sugar in the American diet and what it is doing to our health. I think it probably is directly connected to our rising rates of obesity, whether through leptin resistance or other means. But I don’t think it’s worth worrying about high-fructose corn syrup, per se, while we’re still getting 35% of our calories as sugar.

This whole thing reminds me a little of people who are freaking out about gas prices and dependency on foreign oil.  They’re trading in their cars for models that will improve their gas mileage from 27 to 30 mpg.  But it never occurs to them to drive fewer miles.

Here’s what we all agree on

I am sure that large quantities of fructose will cause health problems in rats and humans. I’m pretty sure that large quantities of any form of sugar will do that. Of course, the specific problems that develop will vary depending on what type of sugar you’re over-consuming. Fructose is hard on the liver while glucose is more challenging to the pancreas.

But rather than argue about which form is more dangerous, what about working the problem from the other end of the equation? I”m talking about the “large quantities” part of the sentence.

Eat less sugar and you probably don’t need to worry about HFCS

The World Health Organization recommends that you limit your intake of added sugars to 10% of calories.  They’re not talking about sugars that are found naturally in whole foods, like fruit or milk. They’re talking about refined sugars in things like candy, baked goods, soft drinks, and condiments.

For most Americans, this would mean cutting their sugar intake by two-thirds.  Whether or not HFCS is really that much worse than other forms of sugar (I’m still not convinced it is), I’m pretty sure that if we simply cut our consumption to a reasonable level, it simply wouldn’t matter.

Call me crazy.