It’s been said we have more food than any other country in the world and more diets to keep them from it. Diet and fitness trends come and go. Currently we are in a low-carb/high-fat craze, yet for many years it was high-carb/low-fat.As a healthcare provider, personal trainer and sports nutritionist, I see many people who are seeking advice on how to lose weight, either to deal with the comorbidities of obesity and/or to feel better about their bodies.

When it comes to weight loss and the quest for a “beach body,” there is a lot of misinformation promulgated by misguided health and fitness professionals, social media and supplement companies that can play on one’s emotions and desire for that “magic” supplement, diet or exercise program to help them melt away the fat. Academics, healthcare providers and fitness professionals can also get duped by poorly designed studies and claims by athletes and celebrities.

Which is a better macro combination? 

Regardless of how you choose to balance your macronutrients (carbohydrates, proteins and fats), the research shows that your success at losing weight and keeping it off will be predicated on biologic and non-biologic factors, such as:

  • Adherence
  • Diet acceptability
  • Satiety
  • Satisfaction
  • Calorie restriction
  • Maintaining lean body mass
  • Being metabolically flexible

Non-biologic factors that increase adherence and diet acceptability include conformity with cultural norms, scientific novelty and social media. In essence, the “best” diet is the one that you resonate with and will follow. (Sacks, F. M.,et al. 2009)

KEY BIOLOGIC FACTORS INCLUDE CALORIE RESTRICTION AND METABOLIC FLEXIBILITY.

Calorie Restriction

Regardless of how macronutrients are manipulated, creating an energy deficit is generally accepted as the best way to reduce body weight and in turn, manage the health-related comorbidities associated with higher body fat.

Numerous studies have shown that significant weight loss has been observed with both low-carbohydrate and low-fat diets. In fact, weight loss differences between popular weight loss diets, such as The Zone, Atkins, Weight Watchers and Ornish, have been shown to be small. These studies provide additional validation in recommending weight loss strategies based on compliance. (Dansinger ML, et al.. 2005) (Johnston BC, et al. 2014)

Maintaining Lean Body Mass

While the comorbidities of obesity are often improved with weight loss diets, many diets also result in the loss of skeletal muscle mass.

In overweight and obese individuals, reductions in muscle mass may impede further weight loss and compromise weight management by down-regulating metabolic processes, including basal metabolic rate.

Consuming a higher protein diet, combined with an energy deficit and resistance training, can attenuate the loss of fat-free mass. In addition, increasing/maintaining muscle by using this strategy has been associated with favorable effects on bone density, glucose regulation, insulin sensitivity, strength, gait, mobility and aging.

(Antonio, J., et al. 2016, Pasiakos, S. M., et al. 2013, Peterson, M. D., et al. 2011)

Metabolic Flexibility

Metabolic flexibility is the capacity to shift between glucose and fat oxidation based on substrate availability and activity. Conversely, metabolic inflexibility is impaired fuel switching and energy dysregulation. Metabolic inflexibility has been implicated in obesity, insulin resistance, type 2 diabetes, metabolic syndrome and aging.

From a weight loss perspective, extreme dietary practices that overemphasize the reliance on one energy substrate, at the expense of another, has the potential over time to down-regulate the ability to be metabolically flexible and in turn, adversely affect normal physiological homeostasis.

Ideally, crosstalk and cooperation between competing substrates (carbohydrates and fats) enables mitochondria to choose the energy source that is most appropriate for a particular physiological state. Preferential selection of glucose or lipids is a homeostatic mechanism that ensures survival.

Burke examined the effects of Low-Carbohydrate/High-Fat (LCHF) diets on metabolism and performance in athletes. She concluded that:

  1. Long-term exposure to LCHF diets down-regulates carbohydrate oxidation during exercise due to a down-regulation of pyruvate dehydrogenase (PDH) and pyruvate dehydrogenase complex (PDC) activity. PDC links fatty acid metabolism, glucose metabolism and the tricarboxylic acid (TCA) cycle (a series of chemical reactions used by all aerobic organisms to generate energy). This impairment of glycogen utilization as an exercise fuel represents a decrease in metabolic flexibility.
  2. LCHF diets reduce exercise capacity and increase both perceived effort and heart rate.
  3. Fat-adaptation strategies may impair exercise performance, especially at higher intensities.
  4. Adaptation to a LCHF diet results in glycogen ‘impairing’ rather than ‘sparing.’

The bottom line: Flexible eating strategies that periodize nutrients based on activity and recovery needs and avoid unnecessary and excessive intakes of any one nutrient are recommended.

It’s worth noting that the Standard American Diet (SAD), which is high in refined carbohydrates and inflammatory fats, is a key driver of metabolic inflexibility.

For obese individuals who have been eating a diet high in refined carbohydrates and who have the signs and symptoms of metabolic inflexibility, the short-term use of a very low-carbohydrate/high-fat diet may be a good strategy to bring these individuals back to homeostasis. Once homeostasis is achieved however, the guidelines outlined below should be followed, as long-term consumption of a high-saturated fat diet may cause hyperglycemia, hyperinsulinemia, glucose intolerance and obesity due to adverse effects on pyruvate dehydrogenase complex activity.

Using the Respiratory Exchange Ratio (RER) as a Macronutrient Guide

The respiratory exchange ratio (RER) is the ratio between the amount of carbon dioxide produced and oxygen used in metabolism.

The RER can be used for estimating the respiratory quotient (RQ), an indicator of which fuel (carbohydrate or fat) is being metabolized to supply the body with energy.

  • The RER is about 0.8 at rest and 1 during intense exercise.
  • RER of 0.70 – fat is the predominant fuel source
  • RER of 0.85 – mix of fat and carbohydrates for fuel
  • RER of 1.00 or above – carbohydrate is the predominant fuel source

As exercise intensity increases, the body prefers to use carbohydrate for energy. Ideally, in a non-exercise state, fat is the primary energy substrate. This is often not the case in individuals who are metabolically inflexible.

Guidelines for Carbohydrate Consumption Based on Activity

  • Low intensity/skill based: 3-5g/kg Body Mass (BM)
  • Moderate intensity: 5-7 g/kg BM
  • Moderate-high intensity (endurance program): 6-10 g/kg BM
  • Extreme: 8-12g/kg BM

For individuals who are not active and are trying to lose weight, carbohydrate consumption can be lowered further than outlined above in order to create a moderate energy deficit.

Guidelines for Protein Consumption For Weight Loss

The minimum protein recommendation (RDA) is 0.8g/kg body weight; however, consuming >2g/kg body weight, in conjunction with resistance training, is more ideal for weight loss and maintaining lean body mass, especially when energy intake is reduced. (Antonio, J., et al. 2016, Longland, T. M. et al. 2016)

Guidelines for Fat Consumption For Weight Loss

Fat intake, like carbohydrates, should be viewed in the context of energy balance. Using a calorie calculator can be helpful in determining an energy deficit and fitting in calories from fat and the other macronutrients.       http://www.calculator.net/calorie-calculator.html

Low-fat diet: 20% fat

High-fat diet (e.g., ketogenic): 75% fat, 20% protein, 5% carbohydrate

Individuals who choose to follow a ketogenic style diet, or those who are metabolically inflexible, should be encouraged to increase their consumption of omega-3 fats, as this has been shown to attenuate some of the adverse effects that a high-fat diet can have on lipid metabolism and blood sugar regulation via PDH activity. (Turvey, E. A. et al. 2005, Chen, C., Yu, X., & Shao, S. 2015)

Some strategies to improve metabolic flexibility include:

  • Exercise to increase lean body mass (resistance training)
  • Exercise to increase mitochondria (aerobic training)
  • Periodize fuel (carbohydrate and fat) selection, including intermittently exercising and recovering in a low glycogen state (train low, sleep low, recover low)
  • Increase protein intake (>2g/kg body weight)
  • Intermittent fasting
  • Very low-carbohydrate/high fat diets for short-term use in those with insulin resistance (during this period, protein consumption should be 20% of total calories in order to minimize gluconeogenesis – the generation of glucose from amino acids).

(Galgani, J. E. et al. 2008, Burke, L. M. 2015, Goodpaster, B. H., & Sparks, L. M. 2017, Muoio, D. M. 2014, Zhang, S., Hulver, M. W., et al. 2014)

Key Points For Evidence-Based Weight Loss and Attaining a Beach Body:

  • Moderate calorie restriction (e.g., a 500 Kcal daily deficit).
  • Eat real foods (plant-based with pasture raised or wild animal products and minimal consumption of refined foods). Increase protein consumption (1.5-2g/kg BM or higher).
  • Match carbohydrate intake to activity and recovery needs. Try a couple of fasted cardio session (e.g., morning session).
  • Weight train to increase lean body mass and fuel your workouts with adequate protein and carbohydrates to promote muscle protein synthesis.
  • Follow a diet with which you feel satisfied and to which you can adhere.
  • Follow the recommendations to become more metabolically flexible based on YOUR specific state of health, not the latest trend.