Slow Digesting Carbohydrates for Fat Loss and Better Performance?

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Consume fewer calories, use more body fat and feel great during exercise – these are the claims behind slow digesting carbohydrates. Before you ditch your typical sports drink in favor of a slow digesting carbohydrate, check out the truth behind each of these lofty claims.

In this post I will cover:

  • One big fat myth – slow digesting carbohydrates won’t help you burn body fat
  • Trying to burn fat during exercise is pointless
  • Fast carbohydrates are better for high-intensity athletes
  • Advice for those on a low carbohydrate diet

According to Generation UCAN, makers of a slow digesting starch (a type of carbohydrate), typical high sugar sports nutrition products cause a rapid increase in energy followed by low blood sugar leading to a sharp crash, leaving you feeling tired with a bad case of the munchies (“post-workout cravings” according to their website). Generation UCAN’s starch will keep your blood sugar levels nice and steady while delivering long-lasting energy for hard-working muscles. The payoff? You need fewer carbohydrates (and therefore calories) to fuel activity and your insulin levels (a hormone that helps store body fat among other functions) are kept low so your body can pull from a larger supply of body fat (multiple times larger than the amount of carbohydrate stored in muscle and liver).

All of this sounds great in theory. Yet none of it holds up in real life.

Typical sports nutrition products do not cause a sharp crash (symptoms of low blood sugar) when consumed before or during exercise (1). Instead, your body will use the sugar pretty quickly to fuel hard working muscles (2). What about post-workout cravings? Typical sports drinks, gels and gummies won’t lead to cravings, despite possible changes in blood sugar, even if you consume them when your body doesn’t need them – when you are sitting on the couch scrolling through Snapchat videos (3).

One Big Fat Myth – Slow Digesting Carbohydrates Won’t Help You Lose Body Fat

Trying to burn fat during exercise is pointless (unless you are a ultra distance athlete and therefore relying on large amounts of fat for energy to run for several hours at a time). Otherwise it doesn’t matter if more fat is used during exercise. What matters most if you want to lose weight? The total amount of calories burned over time.

You are better off burning fat while sitting in front of your computer or sleeping then trying to maximize fat used during exercise. Why? Fat is a slow source of energy – if you are seriously tapping into your fat stores during exercise you aren’t exercising very hard and therefore you aren’t burning very many calories. If you want to make the most of your exercise sessions, burning as many calories as possible, you’ll need carbohydrates to help you sustain your exercise intensity. It’s the difference between walking and sprinting. You have to walk for a much longer period of time to burn as many calories as you will if you are sprinting or doing intervals.

Fast Carbohydrates are Better for Athletic Performance

slow digesting carbohydratesCarbohydrates are the best source of energy to keep up with the calorie demand of high-intensity exercise. The less carbohydrate you have stored in your muscle (stored from the carbohydrate you eat each day), the more your body will rely on carbohydrate consumed during exercise in the form of sports drinks, gels, beans, gummies etc. Fast carbohydrates (the mix of sugars in common sports nutrition products) have been successfully used for decades. Yet some athletes get an upset stomach when exercising. Generation UCAN says their product will lower risk of stomach upset. Unfortunately, a well-designed study found athletes actually had greater stomach upset on UCAN (a slow digesting carbohydrate) than they did on traditional sports nutrition drinks (8). If you don’t want the nitty-gritty science, skip the next section and move to the following paragraph.

In this crossover study (each study subject experienced each type of drink) 10 male cyclists consumed 1) 60 grams of carbohydrate from a typical sports nutrition drink (sucrose and glucose blend) 30 minutes before and 60 grams of carbohydrate per hour during exercise (Sports Drink); 2) 60 grams of carbohydrate from UCAN (hydrothermally-modified starch; HMS) before and 60 grams of carbohydrate per hour during exercise (Isocaloric HMS); 3) 60 grams of carbohydrate from UCAN before and 30 grams of carbohydrate per hour during exercise (Low HMS). They spent three hours exercising (one hour at a moderate pace followed by intervals and sprints). There was no difference in performance between the Sports Drink and High HMS. Both the Sports Drink and High HMS resulted in slightly better performance compared to Low HMS (less carbohydrate during exercise). Consuming UCAN, whether 30 or 60 grams per hour, led to greater incidence of nausea compared to consuming 60 grams of carbohydrate per hour from a typical Sports Drink (8).

Typical carbohydrates used in sports nutrition products are digested quickly and used by muscles right away so you can train harder than you would if you relied on slow carbohydrates. The body can use about 30 – 60 grams of carbohydrate per hour, and possibly up to 90 if a mix of different sugars is used. Fat metabolism kicks in after around 20 minutes of aerobic exercise. “After about two hours of continuous endurance exercise, fat is a major source of energy. However, carbohydrate is still essential. Without enough carbohydrate present there is incomplete burning of fatty acids resulting in ketone bodies as a byproduct. When ketones build up, the body’s pH drops (metabolic acidosis) and the body attempts to compensate via respiratory hyperventilation,” states sports dietitian Sally Hara, MS, RD, CSSD, CDE. You won’t improve performance if you consume slow carbohydrates before or during exercise (5).

Fast carbohydrates are also preferential right after exercise – your body can rapidly replenish carbohydrate stores in muscle for use during her next training session. This is very important for athletes who train more than once over the course of an 8-hour period and also important for those who train again less than 24 hours later (6, 7). Anyone who doesn’t train again less than 24 hours later can re-stock their carbohydrate in muscle by consuming enough carbohydrate in their diet from potatoes, rice, quinoa, and other higher carbohydrate foods.

You can function on fewer carbohydrates. However, “there is a difference between functioning and performing your best. Athletes and high-intensity sports to follow a low carbohydrate diet are more likely to get tired early and make mental errors,” states Hara. If you want to perform well and burn more calories while lowering risk of stomach upset, choose a traditional sports nutrition product instead of being swayed by the false marketing promises behind slow digesting carbohydrate products.

 

References

1 Jeukendrup AE, Killer SC. The myths surrounding pre-exercise carbohydrate feeding. Ann Nutr Metab 2010;57 Suppl 2:18-25.

2 Marmy-Conus N, Fabris S, Proietto J, Hargreaves M. Preexercise glucose ingestion and glucose kinetics during exercise. J Appl Physiol 1996;81:853-857.

3 Schultes B, Panknin A, Hallschmid M, Jauch-Chara K, Wilms B, de Courbiere F, Lehnert H, Schmid SM. Glycemic increase induced by intravenous glucose infusion fails to affect hunger, appetite, or satiety following breakfast in healthy men. Appetite 2016;105(1):562-566.

4 Roberts MD, Lockwood C, Dalbo VJ, Volek J, Kerksick CM. Ingestion of a high-molecular-weight hydrothermally modified waxy maize starch alters metabolic responses to prolonged exercise in trained cyclists. Nutr 2011;27(6):659-665.

5 Burdon CA, Spronk I, Cheng H, O’Connor HT. Effect of Glycemic Index of a Pre-exercise Meal on Endurance Exercise Performance: A Systematic Review and Meta-analysis. Sports Med 2016:1-15.

6 Stephens FB, Roig M, Armstrong G, Greenhaff PL. Post-exercise ingestion of a unique, high molecular weight glucose polymer solution improves performance during a subsequent bout of cycling exercise. J Sports Sci 2007:1-6.

7 Aulin KP, Soderlund K, Hultman F. Muscle glycogen resynthesis rate in humans after supplementation of drinks containing carbohydrates with low and high molecular masses. Eur J Appl Physiol 2000;81:346-351.

8 Bauer DA, Vargas F CS, Bach C, Garvey JA, Ormsbee MJ. Slow-Absorbing Modified Starch before and during prolonged cycling increases fat oxidation and gastrointestinal distress without changing performance. Nutrients 2016;8(392):1-16.

Nutrient Timing: Important for Sprinting & Short Bursts of Activity

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Every endurance and strength athlete knows what they fuel their body with, especially their nutrient timing tactics, will affect their performance and recovery. And, many team sport athletes get this concept as well – even if you make it far on raw talent at some point poor nutrition catches up with you.

Add sprint athletes and those who engage in repeated bouts of short activity (hello hockey players) to the group who can benefit from nutrient timing tactics. Scientists from the Nestle Research Center took healthy, well-trained athletes and had them perform two bouts of sprint cycling with either a protein-carbohydrate supplement (24 grams whey protein, 4.8 grams leucine, 50 grams maltodextrin) or a non-caloric placebo prior to each exercise session. At rest and 15 and 240 minutes post-exercise they took muscle biopsies to evaluate protein synthesis and muscle cell signaling.

Though power output was similar between the groups, post-exercise myofibrillar protein synthetic rate was greater with the supplement than with a placebo. In addition, consuming the protein-carbohydrate drink was beneficial for cell signaling proteins that play a role in protein synthesis. In addition, force-generating, myofibrillar proteins were also greater in the supplemented group indicating that a protein-carbohydrate beverage within proximity to exercise may, over time, translate to increased power and speed.

PS – check out the incredible muscle on Jamaica’s Usain “Lightening” Bolt.