Requesting specific data returns all the associated entities without using the Include()

I am creating a simple web API (MVC) and I am currently using Entity Framework Code First approach. I have the following entities:

Authors, Courses, Institutions

I have set up a relationship in such a way that an author can have N number of courses and N number of institutions. I am writing the following method on the API:

public class PlutoController : ApiController
{
    private readonly PlutoDbContext _context;

    public PlutoController()
    {
        _context = new PlutoDbContext();
    }

    [HttpGet]
    public IHttpActionResult GetAuthors()
    {
        var authors = _context.Authors
            .Where(a => a.AuthorID == 1).ToList();

        return Ok(authors);
    }
}

However, a call to the api returns authors and its associated courses and institutions.

[
{
    "Courses": [
        {
            "CourseSections": [],
            "Tags": [],
            "CourseID": 1,
            "AuthorID": 1,
            "Title": "C# Advanced",
            "Description": "C# Advanced Description",
            "Price": 69,
            "LevelString": "Advanced",
            "Level": 3
        },
        {
            "CourseSections": [],
            "Tags": [],
            "CourseID": 2,
            "AuthorID": 1,
            "Title": "C# Intermediate",
            "Description": "C# Intermediate Description",
            "Price": 49,
            "LevelString": "Intermediate",
            "Level": 2
        },
        {
            "CourseSections": [],
            "Tags": [],
            "CourseID": 3,
            "AuthorID": 1,
            "Title": "Clean Code",
            "Description": "Clean Code Description",
            "Price": 99,
            "LevelString": "Intermediate",
            "Level": 2
        }
    ],
    "Institution": [
        {
            "InstitutionId": 1,
            "AuthorId": 1,
            "InstitutionName": "University of Windsor"
        },
        {
            "InstitutionId": 2,
            "AuthorId": 1,
            "InstitutionName": "Boston University"
        },
        {
            "InstitutionId": 4,
            "AuthorId": 1,
            "InstitutionName": "Arizona State University"
        }
    ],
    "AuthorID": 1,
    "Name": "Bill Gates"
}]

In this, i can see that we are doing some eager loading which is not what i want. How do i just get only the author details?

Here are my generated models: Author

namespace PlutoAPI.Models
{
    using System;
    using System.Collections.Generic;
    using System.ComponentModel.DataAnnotations;
    using System.ComponentModel.DataAnnotations.Schema;
    using System.Data.Entity.Spatial;

    public partial class Authors
    {
        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2214:DoNotCallOverridableMethodsInConstructors")]
        public Authors()
        {
            Institution = new HashSet<Institution>();
            Courses = new HashSet<Courses>();
        }

        [Key]
        public int AuthorID { get; set; }

        [Required]
        [StringLength(255)]
        public string Name { get; set; }

        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
        public virtual ICollection<Institution> Institution { get; set; }

        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
        public virtual ICollection<Courses> Courses { get; set; }
    }
}

Courses:

namespace PlutoAPI.Models
{
    using System;
    using System.Collections.Generic;
    using System.ComponentModel.DataAnnotations;
    using System.ComponentModel.DataAnnotations.Schema;
    using System.Data.Entity.Spatial;

    public partial class Courses
    {
        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2214:DoNotCallOverridableMethodsInConstructors")]
        public Courses()
        {
            CourseSections = new HashSet<CourseSections>();
            Tags = new HashSet<Tags>();
        }

        [Key]
        public int CourseID { get; set; }

        public int AuthorID { get; set; }

        [Required]
        [StringLength(255)]
        public string Title { get; set; }

        [Required]
        [StringLength(8000)]
        public string Description { get; set; }

        public short Price { get; set; }

        [Required]
        [StringLength(50)]
        public string LevelString { get; set; }

        public byte Level { get; set; }

        public virtual Authors Authors { get; set; }

        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
        public virtual ICollection<CourseSections> CourseSections { get; set; }

        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2227:CollectionPropertiesShouldBeReadOnly")]
        public virtual ICollection<Tags> Tags { get; set; }
    }
}

Institution

namespace PlutoAPI.Models
{
    using System;
    using System.Collections.Generic;
    using System.ComponentModel.DataAnnotations;
    using System.ComponentModel.DataAnnotations.Schema;
    using System.Data.Entity.Spatial;

    [Table("Institution")]
    public partial class Institution
    {
        public int InstitutionId { get; set; }

        public int? AuthorId { get; set; }

        [Required]
        [StringLength(50)]
        public string InstitutionName { get; set; }

        public virtual Authors Authors { get; set; }
    }
}