The Exception: Elite Endurance Athletes
For a small subset of the population, specifically elite endurance athletes like marathon runners or triathletes, consuming up to 700 grams of carbohydrates a day is a recognized strategy known as 'carb-loading'. This is not a long-term diet but a temporary, strategic increase in carbohydrate intake over 1-3 days leading up to a major event lasting longer than 90 minutes. The purpose is to maximize muscle and liver glycogen stores, which serve as the body's primary fuel source during prolonged, high-intensity exercise. For example, a 70kg athlete might aim for 10g of carbs per kg of body weight, equaling 700g per day. This process is accompanied by reduced training intensity to ensure maximum glycogen storage. Without the extreme energy demands of this kind of training, this level of carbohydrate intake is simply not needed and can be harmful.
Health Risks for the Average Person
For anyone not engaged in intense, multi-hour daily training, consuming 700g of carbohydrates daily is far too much and poses considerable health risks. When the body takes in more glucose than it can immediately use for energy or store as glycogen, the excess is converted and stored as fat. Chronic overconsumption, especially of refined carbs, can trigger a cascade of negative health effects.
- Weight Gain: The most obvious effect is significant weight gain. Excess glucose that isn't stored as glycogen gets converted into body fat.
- Insulin Resistance and Type 2 Diabetes: Constant high blood sugar levels require the pancreas to produce excessive amounts of insulin. Over time, cells can become resistant to insulin's effects, a precursor to type 2 diabetes.
- Fatigue and Energy Crashes: Refined, simple carbohydrates cause rapid spikes in blood sugar followed by steep crashes. This leads to periods of high energy followed by profound fatigue and mental fogginess.
- Metabolic Syndrome: A high-carb diet, particularly one high in refined sugars, is linked to metabolic syndrome, a cluster of conditions including increased blood pressure, high blood sugar, excess body fat around the waist, and abnormal cholesterol levels.
- Other Issues: Regular bloating, skin issues like acne, and increased cravings for sugary foods are also common side effects of a high, refined carb intake.
The Quality of Carbohydrates Matters
Not all carbohydrates are created equal, and the source of your carbs significantly impacts how your body processes them. Complex carbohydrates, found in whole grains, vegetables, and legumes, are processed slowly and provide sustained energy. Refined carbohydrates, like those in white bread, pastries, and sugary drinks, are quickly digested, leading to blood sugar spikes and crashes.
Complex vs. Simple Carbohydrates
| Feature | Complex Carbohydrates | Simple Carbohydrates |
|---|---|---|
| Source | Whole grains, vegetables, legumes | Sugary drinks, candy, pastries |
| Digestion Speed | Slow, providing sustained energy | Fast, causing rapid blood sugar spikes |
| Nutrient Density | High (Fiber, Vitamins, Minerals) | Low (often called 'empty calories') |
| Satiety | High, keeps you feeling full longer | Low, promotes increased hunger |
General Carb Intake Recommendations
For most people, a balanced diet is recommended, with carbohydrates making up 50-60% of total daily energy intake. The exact amount in grams depends on your body weight and activity level. As outlined by the American College of Sports Medicine, daily needs vary greatly based on lifestyle:
- Light Training (<1 hour/day): 3-5 g/kg of body weight.
- Moderate Training (~1 hour/day): 5-7 g/kg of body weight.
- Endurance Training (1-3 hours/day): 6-10 g/kg of body weight.
- Extreme Endurance (>4 hours/day): 8-12 g/kg of body weight.
Even for athletes, a 700g daily intake is at the high end of these recommendations and typically reserved only for specific pre-event periods, not general training. A sustainable and healthy approach focuses on consuming quality carbohydrates, primarily from whole food sources, in moderation.
Conclusion
In summary, consuming 700 carbs a day is too much for the vast majority of people and is not sustainable for long-term health. While it serves a very specific, temporary purpose for elite endurance athletes engaged in pre-competition carb-loading, it can lead to serious metabolic issues, weight gain, and energy fluctuations for everyone else. The key to a healthy diet is not just the quantity of carbohydrates, but their quality and balance. Focus on nutrient-dense, complex carbs from whole foods to fuel your body effectively and support overall well-being. For personalized advice, consult with a registered dietitian or sports nutritionist to tailor your carb intake to your specific needs.
For more information on the evolving recommendations for athletes' carbohydrate intake, see contemporary perspectives from the Gatorade Sports Science Institute.
