By Paul Stevenson
The first and second part of our Clean Health Fitness Institute 3-part series looked at protein and fat in more detail. This article examines carbohydrate as the third main macronutrient in the human diet.
Carbohydrates can be generally divided into ‘simple’ and ‘complex’. Simple carbohydrates refer to monosaccharides (glucose) and disaccharides (sucrose, lactose). Complex carbohydrates refer to oligosaccharides and polysaccharides (starch). Carbohydrates provide 4kcal per gram, making it less energy dense than fat, which is 9kcal per gram.
Unlike protein and fat, there are no ‘essential’ carbohydrates. The body can function optimally with very low carbohydrate intakes, as evidenced by ketogenic diets, where carbohydrate intake is generally restricted below 100g per day (often lower). The body is able to survive with very few carbohydrates in the diet as the body is able to convert energy from fatty acids into ketones, which can supply the brain and nervous system with energy.
However, unless being in ketosis is desirable, it is recommended that carbohydrate intake is kept above 100g per day. The optimal amount of carbohydrate in a person’s diet will vary greatly depending on activity levels. The ratio of carbohydrate and fat in the diet does not matter too much on a broad level, and often comes down to individual preference. Part of the decision-making process should revolve around how well someone tolerates carbohydrates. Normal carbohydrate tolerance is associated with an appropriate insulin release given the individual’s insulin sensitivity.
For clients with the predominant goal of fat loss, I like to incorporate larger amounts of carbohydrate around workouts, with minimal intakes at other times. Nutrient partitioning is much better in the post-workout period. This means the additional energy provided by the carbohydrate is used to repair and build muscle tissue.
So, for someone eating 4 times per day, and training at 5pm with the goal of losing body fat, a typical day may look something like this:
- 7.00am: Breakfast – Protein & Fats: 2 whole eggs, 2 egg whites with 50g smoked salmon & spinach.
- 11.00am: Lunch – Protein & Fats: 120g Grilled Chicken Breast, Avocado, Capsicum & broccoli
- 3.00pm: Mid-Afternoon – Protein & Fats: Salmon Fillet and Asparagus with a drizzle of olive oil
- 7.00pm: Post-Workout/Dinner – Protein & Carbohydrate: Grilled Barramundi with Sweet Potato, Green salad and a banana.
Fibre intake is extremely important for optimal health and most dietary fibre can be found in carbohydrate-containing foods, such as vegetables, fruits, whole grains and legumes etc.
Recommended daily fibre intakes for men are 38g and women 25g (Gropper & Smith, 2012), however most people in western countries fall way short of these amounts. If embarking on very low carbohydrate or ketogenic diets, it may be wise to take some supplemental fibre, as it is unlikely you will obtain optimal amounts from diet alone.
Carbohydrates have been somewhat demonised of late due to some mis-leading claims surrounding the effect of carbohydrates on the hormone insulin. I have already written an article debunking the insulin-hypothesis so I will not go into this subject in any detail here. The point I want to make here is that when it comes to losing body fat the two most important factors to consider are:
- Total Calorie intake
So essentially, if someone wishes to lose body fat, they need to ensure calorie intake is at an appropriate level and that this level can be adhered to in the long-term. Some people can adhere really well to low-carbohydrate diets. Other people find moderate to high carbohydrate intake to be optimal. No single macronutrient is driving the obesity epidemic; overall calorie intake is.
So when deciding an appropriate level of carbohydrate intake for a client or yourself, the following factors will need to be considered:
- Body Fat Percentage: Generally speaking, the higher a person’s body fat percentage, the lower their carbohydrate needs. Nutrient partitioning is much poorer in overweight and obese clients so I generally keep carbohydrate intake to a minimum until more healthy body fat levels are reached.
- Goal: The client goal is of extreme importance when setting carbohydrate intake. If someone is looking to build muscle tissue, then more energy will be required, as building muscle is a very energy-costly process.
- Training Phase: Generally speaking, the more volume someone has in their workouts, the more total work they are performing, the greater need to replenish glycogen stores after training.
- Activity levels/Lifestyle: Someone who is more active in day-to-day life will have a much greater need for carbohydrates than someone more sedentary. Therefore what someone does for a job, how they travel to work, what hobbies they have are all important pieces of information to know & factor in to overall intake.
Take Home Points:
- Match carbohydrate intake to activity levels and overall carbohydrate tolerance
- Carbohydrates a great source of fibre – ensure you are meeting the recommended intakes (38g men/28g women)
- Due to association between obesity and insulin resistance, low carbohydrate diets generally work well for obese/overweight clients in the first 6-12 months
Gropper, S & Smith, J, “Advanced Nutrition and Human Metabolism”, 2012.