Understanding Diet Basics to Cut Clients’ Confusion, Part One

Personal trainers should know the basics of the most typical diets to guardrail their clients and know when to refer to a registered dietician.

Introduction

If you’re confused about the different types of diets out there, you’re not alone. Just imagine how much more confused your clients may be as they navigate the waters of diets. We’ve all had clients tell us about a friend who proclaimed one diet or another had terrific results. This often leads clients to think there is something magical or powerful about a specific diet. 

It isn’t always as simple as following your friend’s diet. Health conditions, such as obesity, diabetes, and heart disease, can add to the confusion and complexity of determining diet effectiveness. Personal trainers should refer to a registered dietician in these more complex medical issues.

However, most diets have a few things in common that work together to help you eat healthier and lose weight, and the good news is that you don’t necessarily have to “diet” to improve these. As personal trainers, it is entirely within our scope to have a casual conversation with our clients about these points below.

• Increased awareness of eating decisions (are clients overeating for a specific reason? If so, what?)
• Food intake timing rules (are clients’ meal times too varied, leading to over or under-eating at certain times of the day?)
• Reduced caloric intake (being aware of how many calories are in some foods)
• Improved quality of foods (being more aware of adding high quality foods)
• Improved proportions of macronutrients (increasing veggies and decreasing simples carbs, for example)

These characteristics lead to positive change, not the diet itself. Looking at the list above, you don’t necessarily have to pick a “diet to follow” to improve your eating and move closer to your health goals. You could instead focus on one or two of those characteristics rather than making a drastic and sometimes intimidating change to your diet. 

In addition to mindful eating tips, personal trainers should know the basics of the most apparent diets to dispel myths, confusion, unsafe practices, and answer any questions their clients may have. 

This article will discuss the latest research on many popular diets. Some of the research discussed will consider the most impactful diseases, such as diabetes, obesity, and heart disease. 

Low-Carbohydrate vs Low-Fat Diets

Typical low-carbohydrate diets, such as the ketogenic or Atkins diet, are popular, but how do they compare to low-fat diets like vegan, vegetarian, and other plant-based diets for weight loss? According to multiple reviews and randomized control trials, both categories of diets result in similar changes in weight loss (Sandouk & Lansang, 2017; Apekey, et al., 2022; Wachsmuth, et al., 2022; Gardner, et al., 2017; Blaak et al., 2021). 

This isn’t to say that there are no differences in other specific outcomes, like inflammation or gut health. Even though there are similar weight loss outcomes, each diet category appears to have unique effects on specific health markers. The low-fat diet may be more effective at lowering total and LDL cholesterol, and the low-carb diet may be more effective at lowering HbA1c (Wachsmuth et al., 2022).

If your goal is just weight loss, then pick the diet that works best for you. You can even try both. If you have an additional goal such as lowering blood lipids or blood sugar, then a diet that is specifically low carb or low fat may have a slight advantage. 

Low vs Balanced Carbohydrate Diets

Low-carb diets comprise 5% to 30% of the total daily calories, whereas a balanced-carb diet ranges from 40% to 60%. A meta-analysis of 58 randomized control trials examined the differences in weight loss and cardiovascular health and risk factors in 5,118 adults in high-income countries who were overweight or living with obesity, without or with T2DM, and with or without cardiovascular conditions or risk factors (Naude et al., 2022).

The analysis found that people following a low‐carbohydrate diet show similar weight-loss compared to those following balanced‐carbohydrate diets for up to two years. Similarly, results show little to no difference between the diets for changes in heart disease risks, like diastolic blood pressure, HbA1c, and LDL cholesterol up to two years.

The Importance of Carbohydrate Quality Over Composition

If differing macronutrient compositions, such as low-carb vs. low-fat, have little difference in weight loss outcomes, perhaps more focus should be had on dietary quality. When controlling for daily caloric intake, diets varying in quality or nutritional density have diverse effects on hormones, metabolic pathways, gene expression, and the gut microbiome that influences weight gain (Ludwig & Ebbeling, 2018).

One research article writes that when the focus is on eating foods that are “low carb” or “low fat”, food companies will produce a low-carb version that has more fat, with low nutritional value while remaining at a similar calorie level (Sievenpiper, 2020).

Many nutrition researchers recommend focusing on carbohydrate quality rather than quantity, providing greater dietary flexibility (Sievenpiper, 2020; Giugliano et al., 2018; Blaak et al., 2021). However, they acknowledge that some people may benefit better from low carb, if they substitute the carbs for healthy alternatives from high-quality unsaturated fats and plant-protein for carbohydrates. 

If a high-carbohydrate diet is preferred, emphasize high-quality carbohydrate foods such as whole grains (especially oats and barley), pulses, or fruit; low GI and GL; or high fiber (especially viscous fiber sources) (Sievenpiper, 2020).

The Importance of Fat Quality Over Composition

Similarly to the importance of emphasizing quality carbs over specific amounts of carbs in the diet, the same can be said about dietary fat. Since the research shows that low-fat or high-fat diets don’t show differences in weight loss, the right types of dietary fat should be emphasized. 

A recent scoping review of 59 systematic reviews on dietary fat quality and outcomes concluded that saturated fat should be limited, trans fats should be avoided, and mono and polyunsaturated fats should be prioritized as the primary sources of fat (Schwingshackl et al., 2022). The review found that most dietary guidelines recommend a total fat intake of 30-35% of daily caloric intake. Recommendations daily % of calories on specific fats are:

• Saturated fats 7-11% 
• Trans fats 0-2%
• Monounsaturated fatty acids 10-25%
• Polyunsaturated fatty acids 5-11%

For the general population, less than 10% of total daily calories should come from saturated fat, or 22 g for 2,000 daily calories (Maki, 2021). For populations with dyslipidemia or atherosclerotic cardiovascular disease, 5-6% should come from saturated fat, 11-12g for 2,000 daily calories (Maki, 2021). Foods high in saturated fats are usually non-lean animal meats, cheeses, butter, cream, dairy-based desserts, and coconuts.

Diets that emphasize intakes of fruits and vegetables, whole grains, nuts, seeds, legumes, non-tropical oils, and lean protein foods will usually contain high-quality dietary fat. Choose low-fat dairy products, choose lean meat, and fish. These food-based recommendations are reasonable and leave plenty of room for variation in the diet (Christensen et al.)

In summary, the most crucial factor isn’t the total fat quantity but the quality of the fat. In practical terms, we should, for example, choose low-fat over high-fat dairy products; choose lean meat and lean meat products over high-fat variants; choose cooking oils, liquid margarine, and soft margarine over hard margarine and butter; and eat fish two to three times a week, including some fatty fish. These food-based recommendations are reasonable and leave plenty of room for variation in the diet.

Diet plays a critical role in weight loss and other lifestyle factors like exercise and behavior modification. Many types of diets vary in carb, fat, and protein composition. According to many studies, there isn’t a single optimal weight-loss diet. Current dietary research allows for flexibility in the distribution of macronutrients as long as they are from quality sources.

In part two, we’ll cover the basics of a few other dietary strategies, such as intermittent fasting, high protein, and more. With a basic knowledge of diets, personal trainers can play a significant role in reducing their clients’ confusion regarding dietary behaviors, especially when access to a registered dietician is lacking. 

References

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2. Apekey TA, Maynard MJ, Kittana M, Kunutsor SK. Comparison of the Effectiveness of Low Carbohydrate Versus Low Fat Diets, in Type 2 Diabetes: Systematic Review and Meta-Analysis of Randomized Controlled Trials. Nutrients. 2022 Oct 19;14(20):4391. doi: 10.3390/nu14204391. PMID: 36297075; PMCID: PMC9609579.
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