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Can sugar really harm you?

Dr Paul Henning PhD, CSCS, CISSN

Does sugar cause metabolic diseases?

Can you get away with consuming sugar as long as you control your calories?

Is there a time when you can consume sugar without doing yourself any harm?

Does sugar make you fat or gain weight?

Sure, most people don’t want to gain weight. But simply not gaining weight does not tell you the whole story of how a food impacts you, your body, or your health.

In this article we will answer those questions with the research we have available to us today.

But, before we dive in there are a few things we should get cleared up.

What exactly is sugar?

First of all, ALL carbohydrate is sugar.

Whether you are consuming apples, broccoli, bread, or chocolate cookies you are providing your body with sugar. These foods get broken down to simple sugars (e.g.

glucose or fructose) to be utilized as energy in the cells of our body.

Blasphemy!

No, actually it is science.

Clarification of what kind of sugar we are discussing is key.

In this article we will talk about ‘added sugar’.

The term ‘added sugar’ refers to sugars not naturally-occurring in foods and consists mostly of sucrose and high fructose corn syrup. These sugars may be found in beverages as well as solid foods.

Sugar and metabolic disease: A look at the evidence

A recent study showed that in only 9 days after the removal of added sugar from the diets of children; improvements in blood pressure, cholesterol levels and triglyceride measures were demonstrated (6) .

Glucose tolerance and insulin responses were also improved.

This happened without weight loss.

This happened without changing calories or macronutrient composition of their diets. (No, they did not cut carbohydrate consumption).

So no, the scale did not change, but yes their health changed.

The markers of metabolic disease (cardiovascular disease, type 2 diabetes and non-alcoholic fatty liver disease) that these children were displaying were significantly reduced after removing the added sugars they were consuming in their everyday lives.

So yes, the type of sugar you consume matters.

The prevalence of metabolic disease is strongly associated with being overweight and obese. This has perpetuated the widespread belief that diet impacts metabolic disease solely through the effects of excess body weight and fat (8) .

Of course, the sugar industry are heavily campaigning to reinforce this belief and “educate” the public that the only dietary culprit is excess calories (1) !
But, as you have just seen above; the consumption of added sugar does have a
different impact on health even when calories are not consumed in excess (6) .

High fructose corn syrup directly causes dysregulation of lipid (i.e. fat) and carbohydrate metabolism. Considerable evidence shows the intake of added sugars and/or sugar-sweetened beverages are associated with unfavorable lipid levels, insulin resistance, fatty liver, type 2 diabetes, cardiovascular disease, and visceral adiposity (8) .

As such the public and health care providers need to be informed accordingly.

Can I have sugar if I don’t overeat?

Results from recent evidence show that consuming added sugar increases risk factors for metabolic disease when consumed with a diet that does not provide excess calories (2, 7) .

Here is an interesting and noteworthy side note! The research that suggests there are no health effects associated with consumption of added sugar were industry-funded or conducted by investigators who have received consulting fees from industries with a strong financial interest in maintaining high levels of sugar consumption (8) .

Definitely take this with a grain of salt!! Oftentimes, we need to look at who is funding the research and their ulterior motives.

There is both epidemiological data, clinical data and plausible mechanisms from diet intervention studies that convey strong support for a direct causal/contributory role of sugar in the increase in metabolic disease and for an indirect causal/contributory role facilitated by sugar consumption promoting body weight and fat gain (8) .

Sugar addiction?


Recent research found that compared with consumption of a low glycemic index meal, a meal high in refined carbohydrates decreased plasma glucose, increased hunger for additional high sugar foods, and selectively stimulated brain regions 4 hours after eating, which is a critical time point influencing eating behavior at the next meal (5) .

This did not happen when those same participants consumed a low glycemic index meal.

These results demonstrate highly processed carbohydrates (i.e. white bread, concentrated sugar) alter brain activity in ways that make you crave them even more (5) .

It should be noted that both the high and low GI meals contained the same amount of calories, and macronutrients. That means, the exact same amount of carbohydrate, protein, and fat. Again showing that it isn’t just the amount of carbohydrate you consume that matters, it matters what type of carbohydrate you consume.

So that means you should probably remove sugar from your diet, right?

Well, not necessarily.

The importance of the Metabolic Window

Just as it is important for you to be clear about what type of sugar and carbohydrates you are eating, it is equally as important to be clear about when you are eating them.

The chemical and hormonal environment within your body is quite different when you are exercising and when you are at rest.

In fact, there is a period of time around your training that your body responds differently to nutrients. This is called the Metabolic Window.

During this period (~3 hours) following intense exercise certain nutrients are more readily taken up into muscle tissue; specifically sugar, and high GI carbohydrates.

One of the main reasons for this is due to the enhanced activity and sensitivity of GLUT4 protein (glucose transport protein).

You can think of GLUT4 as a gatekeeper of sorts. It ‘opens the door’ and allows carbohydrates to move into the muscle cells instead of going elsewhere to be stored as fat or simply staying in circulation and resulting in elevated blood sugar.

Muscular contractions, particularly the ones you experience when you are performing resistance training, increase the activity of GLUT4 [4]. In fact, there is a direct association between GLUT4 protein expression and muscle recruitment.

This basically means that training intensely with resistance exercise enhances the sensitivity of this important protein and allows glucose to be taken up much more efficiently in the hours following a resistance exercise session.

In other words you don’t experience the ‘down side’ to consuming carbohydrates instead it means you experience enhanced recovery and better results from your training.

What is Insulin Resistance?

What does it mean to say someone is insulin resistant?

To simplify things it means that their body does not respond appropriately to small increases in insulin; their bodies require large increases in insulin to aid in shuttling carbohydrate from the blood stream into tissues (fat, muscle, liver).

Again GLUT4 comes into play.

GLUT-4 is predominantly located inside the muscle cell but moves to the cell membrane by the action of insulin. Insulin resistance causes problems in this GLUT-4 action and seriously compromises control of blood glucose.

Can exercise help?

It is well known from research that exercise improves insulin-stimulated glucose transport in the muscle that is recruited during training (4) . Insulin-stimulated glucose uptake was about 90% greater in a trained obese model (3) !

That is huge!!

This clearly explains the importance and the reasons behind why exercise prevents type-2 diabetes and how exercise can turn around the symptoms in someone who already has type 2 diabetes.

Although intense cardio will enhance insulin resistance, don’t forget about intense resistance exercise! Research shows the following amazing benefits from this form of exercise:

  • Improved glycemic control due to increased muscle glycogen (which is the storage form of glucose inside your muscles)
  • Enhances sensitivity and control of GLUT 4.
  • Increased utilization of glucose.

Take home points

  • There is considerable evidence showing that sugar causes metabolic disease even if calories are controlled and not in excess!
  • There is considerable evidence showing a contributory role facilitated by sugar consumption promoting body weight and fat gain.
  • Intense resistance exercise greatly enhances GLUT4 protein content which enhances glycemic control and utilization of glucose.

References
1. Are all calories created equal? An analysis of hte Coca-Cola Company's
communication in the fight against obesity. April 2015.

2. Black RN, Spence M, McMahon RO, Cuskelly GJ, Ennis CN, McCance DR,Young IS, Bell PM, and Hunter SJ. Effect of eucaloric high- and low-sucrose diets with identical macronutrient profile on insulin resistance and vascular risk: a randomized controlled trial. Diabetes 55: 3566-3572, 2006.

3. Brozinick JT, Jr., Etgen GJ, Jr., Yaspelkis BB, 3rd, Kang HY, and Ivy JL. Effects of exercise training on muscle GLUT-4 protein content and translocation in obese Zucker rats. The American journal of physiology 265: E419-427, 1993.

4. Ivy JL. Muscle insulin resistance amended with exercise training: role of GLUT4 expression. Medicine and science in sports and exercise 36: 1207-1211, 2004.

5. Lennerz BS, Alsop DC, Holsen LM, Stern E, Rojas R, Ebbeling CB, Goldstein JM, and Ludwig DS. Effects of dietary glycemic index on brain regions related to reward and craving in men. The American journal of clinical nutrition 98: 641-647, 2013.

6. Lustig RH, Mulligan K, Noworolski SM, Tai VW, Wen MJ, Erkin-Cakmak A, Gugliucci A, and Schwarz JM. Isocaloric fructose restriction and metabolic improvement in children with obesity and metabolic syndrome. Obesity (Silver Spring) 24: 453-460, 2016.

7. Stanhope KL. Role of fructose-containing sugars in the epidemics of obesity and metabolic syndrome. Annual review of medicine 63: 329-343, 2012.

8. Stanhope KL. Sugar consumption, metabolic disease and obesity: The state of the controversy. Crit Rev Clin Lab Sci 53: 52-67, 2016.

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